chore(deps): Bump github.com/golang/protobuf from 1.5.2 to 1.5.3 (#926)

Bumps [github.com/golang/protobuf](https://github.com/golang/protobuf) from 1.5.2 to 1.5.3.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a href="https://github.com/golang/protobuf/releases">github.com/golang/protobuf's releases</a>.</em></p>
<blockquote>
<h2>v1.5.3</h2>
<p>Notable changes</p>
<p>*( <a href="https://github-redirect.dependabot.com/golang/protobuf/issues/1363">#1363</a>) jsonpb: accept 'null' as a valid representation of NullValue in unmarshal</p>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a href="https://github.com/golang/protobuf/commit/5d5e8c018a13017f9d5b8bf4fad64aaa42a87308"><code>5d5e8c0</code></a> Merge pull request <a href="https://github-redirect.dependabot.com/golang/protobuf/issues/1363">#1363</a> from neild/jsonnull</li>
<li><a href="https://github.com/golang/protobuf/commit/37828f962262b5a0f3d9560c429a14d96c711a21"><code>37828f9</code></a> jsonpb: accept 'null' as a valid representation of NullValue in unmarshal</li>
<li>See full diff in <a href="https://github.com/golang/protobuf/compare/v1.5.2...v1.5.3">compare view</a></li>
</ul>
</details>
<br />


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</details>

go.mod

@@ -21,7 +21,7 @@ require (
 	github.com/gogo/gateway v1.1.0
 	github.com/gogo/protobuf v1.3.3
 	github.com/golang/mock v1.6.0
-	github.com/golang/protobuf v1.5.2
+	github.com/golang/protobuf v1.5.3
 	github.com/gorilla/handlers v1.5.1
 	github.com/gorilla/mux v1.8.0
 	github.com/grpc-ecosystem/go-grpc-middleware v1.3.0

go.sum

@@ -439,8 +439,9 @@ github.com/golang/protobuf v1.4.2/go.mod h1:oDoupMAO8OvCJWAcko0GGGIgR6R6ocIYbsSw
 github.com/golang/protobuf v1.4.3/go.mod h1:oDoupMAO8OvCJWAcko0GGGIgR6R6ocIYbsSw735rRwI=
 github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
 github.com/golang/protobuf v1.5.1/go.mod h1:DopwsBzvsk0Fs44TXzsVbJyPhcCPeIwnvohx4u74HPM=
-github.com/golang/protobuf v1.5.2 h1:ROPKBNFfQgOUMifHyP+KYbvpjbdoFNs+aK7DXlji0Tw=
 github.com/golang/protobuf v1.5.2/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
+github.com/golang/protobuf v1.5.3 h1:KhyjKVUg7Usr/dYsdSqoFveMYd5ko72D+zANwlG1mmg=
+github.com/golang/protobuf v1.5.3/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
 github.com/golang/snappy v0.0.0-20180518054509-2e65f85255db/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
 github.com/golang/snappy v0.0.1/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
 github.com/golang/snappy v0.0.3/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=