Bump coverlet.collector from 3.0.2 to 3.0.3 in /Rx.NET/Source

Bumps [coverlet.collector](https://github.com/coverlet-coverage/coverlet) from 3.0.2 to 3.0.3.
- [Release notes](https://github.com/coverlet-coverage/coverlet/releases)
- [Commits](https://github.com/coverlet-coverage/coverlet/commits)

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

Author: dependabot-preview[bot]

Rx.NET/Source/Directory.build.props

@@ -32,7 +32,7 @@
   </ItemGroup>
 
   <ItemGroup Condition="'$(IsTestProject)' == 'true'">
-    <PackageReference Include="coverlet.collector" Version="3.0.2" />
+    <PackageReference Include="coverlet.collector" Version="3.0.3" />
   </ItemGroup>
 
 </Project>