Bump Polyfill from 6.10.0 to 7.0.0 (#280)

Bumps [Polyfill](https://github.com/SimonCropp/Polyfill) from 6.10.0 to
7.0.0.
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/SimonCropp/Polyfill/commit/91ef403157f3562ae006ead84b1b9d636925826d"><code>91ef403</code></a>
remove IEnumerable.Except&lt;TSource&gt;(params TSource items) (<a
href="https://redirect.github.com/SimonCropp/Polyfill/issues/236">#236</a>)</li>
<li><a
href="https://github.com/SimonCropp/Polyfill/commit/fed2a9dcff7cdaeeb7abde8a448ed43d667e7f9c"><code>fed2a9d</code></a>
.</li>
<li><a
href="https://github.com/SimonCropp/Polyfill/commit/0bfabfa3a178f4ff4793ff25df4bd885c2761e6c"><code>0bfabfa</code></a>
Revert &quot;remove IEnumerable.Except&lt;TSource&gt;(params TSource[]
items)&quot;</li>
<li><a
href="https://github.com/SimonCropp/Polyfill/commit/b3fb599d43558366ab641f3242b8f53871920866"><code>b3fb599</code></a>
remove IEnumerable.Except&lt;TSource&gt;(params TSource[] items)</li>
<li><a
href="https://github.com/SimonCropp/Polyfill/commit/0f45e7c979d7d8f16a0f58fa200a58106146caf2"><code>0f45e7c</code></a>
cleanup</li>
<li><a
href="https://github.com/SimonCropp/Polyfill/commit/1adcd7e9c12bffcf390dc066acf598801f711e3f"><code>1adcd7e</code></a>
simplify IsHeldByCurrentThread</li>
<li><a
href="https://github.com/SimonCropp/Polyfill/commit/84f7177773d0edcfa297d9af6ba0c5cb4f64526d"><code>84f7177</code></a>
refs</li>
<li><a
href="https://github.com/SimonCropp/Polyfill/commit/108c54a6db23741cd02c3613f2b9d547fd85348c"><code>108c54a</code></a>
typo</li>
<li><a
href="https://github.com/SimonCropp/Polyfill/commit/b26ef012f7fd47e984db64cf95d4a2e4add616df"><code>b26ef01</code></a>
Update global.json</li>
<li><a
href="https://github.com/SimonCropp/Polyfill/commit/3b0fd698f8ea089dbab00e781f96cdadcecfcc7c"><code>3b0fd69</code></a>
Update TaskCompletionSource.cs</li>
<li>Additional commits viewable in <a
href="https://github.com/SimonCropp/Polyfill/compare/6.10.0...7.0.0">compare
view</a></li>
</ul>
</details>
<br />


[![Dependabot compatibility
score](https://dependabot-badges.githubapp.com/badges/compatibility_score?dependency-name=Polyfill&package-manager=nuget&previous-version=6.10.0&new-version=7.0.0)](https://docs.github.com/en/github/managing-security-vulnerabilities/about-dependabot-security-updates#about-compatibility-scores)

Dependabot will resolve any conflicts with this PR as long as you don't
alter it yourself. You can also trigger a rebase manually by commenting
`@dependabot rebase`.

[//]: # (dependabot-automerge-start)
[//]: # (dependabot-automerge-end)

---

<details>
<summary>Dependabot commands and options</summary>
<br />

You can trigger Dependabot actions by commenting on this PR:
- `@dependabot rebase` will rebase this PR
- `@dependabot recreate` will recreate this PR, overwriting any edits
that have been made to it
- `@dependabot merge` will merge this PR after your CI passes on it
- `@dependabot squash and merge` will squash and merge this PR after
your CI passes on it
- `@dependabot cancel merge` will cancel a previously requested merge
and block automerging
- `@dependabot reopen` will reopen this PR if it is closed
- `@dependabot close` will close this PR and stop Dependabot recreating
it. You can achieve the same result by closing it manually
- `@dependabot show <dependency name> ignore conditions` will show all
of the ignore conditions of the specified dependency
- `@dependabot ignore this major version` will close this PR and stop
Dependabot creating any more for this major version (unless you reopen
the PR or upgrade to it yourself)
- `@dependabot ignore this minor version` will close this PR and stop
Dependabot creating any more for this minor version (unless you reopen
the PR or upgrade to it yourself)
- `@dependabot ignore this dependency` will close this PR and stop
Dependabot creating any more for this dependency (unless you reopen the
PR or upgrade to it yourself)


</details>

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

src/Directory.Build.props

@@ -34,7 +34,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Polyfill" Version="6.10.0" PrivateAssets="All" />
+    <PackageReference Include="Polyfill" Version="7.0.0" PrivateAssets="All" />
   </ItemGroup>
 
   <ItemGroup>