Bump Google.Protobuf from 3.15.7 to 3.15.8 (#4927)

Bumps [Google.Protobuf](https://github.com/protocolbuffers/protobuf) from 3.15.7 to 3.15.8.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.15.7...v3.15.8)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

src/common.props

@@ -14,7 +14,7 @@
     <HyperionVersion>0.9.17</HyperionVersion>
     <NewtonsoftJsonVersion>13.0.1</NewtonsoftJsonVersion>
     <NBenchVersion>2.0.1</NBenchVersion>
-    <ProtobufVersion>3.15.7</ProtobufVersion>
+    <ProtobufVersion>3.15.8</ProtobufVersion>
     <NetCoreTestVersion>netcoreapp3.1</NetCoreTestVersion>
     <NetTestVersion>net5.0</NetTestVersion>
     <NetFrameworkTestVersion>net471</NetFrameworkTestVersion>