Bump MSBuild.Sdk.Extras from 3.0.38 to 3.0.44 in /Rx.NET/Source

Bumps [MSBuild.Sdk.Extras](https://github.com/novotnyllc/MSBuildSdkExtras) from 3.0.38 to 3.0.44.
- [Release notes](https://github.com/novotnyllc/MSBuildSdkExtras/releases)
- [Commits](novotnyllc/MSBuildSdkExtras@v3.0.38...v3.0.44)

---
updated-dependencies:
- dependency-name: MSBuild.Sdk.Extras
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

Rx.NET/Source/global.json

@@ -1,5 +1,5 @@
 {
   "msbuild-sdks": {
-    "MSBuild.Sdk.Extras": "3.0.38"
+    "MSBuild.Sdk.Extras": "3.0.44"
   }
 }