chore(deps): update dependency google-cloud-kms to v2.2.0 (#57)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [google-cloud-kms](https://togithub.com/googleapis/python-kms) | minor | `==2.0.0` -> `==2.2.0` |

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### Release Notes

<details>
<summary>googleapis/python-kms</summary>

### [`v2.2.0`](https://togithub.com/googleapis/python-kms/blob/master/CHANGELOG.md#&#8203;220-httpswwwgithubcomgoogleapispython-kmscomparev210v220-2020-09-16)

[Compare Source](https://togithub.com/googleapis/python-kms/compare/v2.1.0...v2.2.0)

##### Features

-   regenerate client lib to pick up new mtls env ([#&#8203;55](https://www.github.com/googleapis/python-kms/issues/55)) ([4d62c19](https://www.github.com/googleapis/python-kms/commit/4d62c19d2f0f7c597214f2b39dfecb85f9d75a58))

##### Documentation

-   add crypto_key_path_path method rename to UPGRADING.md ([#&#8203;45](https://www.github.com/googleapis/python-kms/issues/45)) ([81db5d9](https://www.github.com/googleapis/python-kms/commit/81db5d90112092772b83aec57e2358088ed88e0d)), closes [#&#8203;43](https://www.github.com/googleapis/python-kms/issues/43)

### [`v2.1.0`](https://togithub.com/googleapis/python-kms/blob/master/CHANGELOG.md#&#8203;210-httpswwwgithubcomgoogleapispython-kmscomparev201v210-2020-08-27)

[Compare Source](https://togithub.com/googleapis/python-kms/compare/v2.0.1...v2.1.0)

##### Features

-   accept custom client_info ([#&#8203;41](https://www.github.com/googleapis/python-kms/issues/41)) ([6688e80](https://www.github.com/googleapis/python-kms/commit/6688e80aa4db74980d4a6194519c814a22cde177))

##### [2.0.1](https://www.github.com/googleapis/python-kms/compare/v2.0.0...v2.0.1) (2020-08-24)

##### Bug Fixes

-   add system test back ([#&#8203;39](https://www.github.com/googleapis/python-kms/issues/39)) ([fc5a720](https://www.github.com/googleapis/python-kms/commit/fc5a720d93ba41cd2616c7c9c8012d9a3e8f4a9c))

##### Documentation

-   Generate using new common.py_samples() synthtool functionality ([#&#8203;35](https://www.github.com/googleapis/python-kms/issues/35)) ([90097bc](https://www.github.com/googleapis/python-kms/commit/90097bca7660f148f36e009f70d108404efa5308))

### [`v2.0.1`](https://togithub.com/googleapis/python-kms/blob/master/CHANGELOG.md#&#8203;201-httpswwwgithubcomgoogleapispython-kmscomparev200v201-2020-08-24)

[Compare Source](https://togithub.com/googleapis/python-kms/compare/v2.0.0...v2.0.1)

</details>

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kms/snippets/requirements.txt

@@ -1,2 +1,2 @@
-google-cloud-kms==2.0.0
+google-cloud-kms==2.2.0
 cryptography==3.1.1