Bump Google.Protobuf from 3.11.4 to 3.12.1 (#4423)

Bumps [Google.Protobuf](https://github.com/protocolbuffers/protobuf) from 3.11.4 to 3.12.1.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.11.4...v3.12.1)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

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

src/common.props

@@ -14,7 +14,7 @@
     <HyperionVersion>0.9.15</HyperionVersion>
     <NewtonsoftJsonVersion>12.0.3</NewtonsoftJsonVersion>
     <NBenchVersion>2.0.1</NBenchVersion>
-    <ProtobufVersion>3.11.4</ProtobufVersion>
+    <ProtobufVersion>3.12.1</ProtobufVersion>
     <NetCoreTestVersion>netcoreapp3.1</NetCoreTestVersion>
     <NetFrameworkTestVersion>net461</NetFrameworkTestVersion>
     <NetStandardLibVersion>netstandard2.0</NetStandardLibVersion>