Bump coverlet.collector from 3.1.0 to 3.1.1 in /Rx.NET/Source

Bumps [coverlet.collector](https://github.com/coverlet-coverage/coverlet) from 3.1.0 to 3.1.1.
- [Release notes](https://github.com/coverlet-coverage/coverlet/releases)
- [Commits](https://github.com/coverlet-coverage/coverlet/commits)

---
updated-dependencies:
- dependency-name: coverlet.collector
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

Rx.NET/Source/Directory.build.props

@@ -32,7 +32,7 @@
   </ItemGroup>
 
   <ItemGroup Condition="'$(IsTestProject)' == 'true'">
-    <PackageReference Include="coverlet.collector" Version="3.1.0" />
+    <PackageReference Include="coverlet.collector" Version="3.1.1" />
   </ItemGroup>
 
 </Project>