Bump MSBuild.Sdk.Extras from 2.0.54 to 2.1.2 in /Ix.NET/Source

Bumps [MSBuild.Sdk.Extras](https://github.com/novotnyllc/MSBuildSdkExtras) from 2.0.54 to 2.1.2.
- [Release notes](https://github.com/novotnyllc/MSBuildSdkExtras/releases)
- [Commits](https://github.com/novotnyllc/MSBuildSdkExtras/compare/v2.0.54...v2.1.2)

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

Ix.NET/Source/global.json

@@ -1,5 +1,5 @@
 {
   "msbuild-sdks": {
-    "MSBuild.Sdk.Extras": "2.0.54"
+    "MSBuild.Sdk.Extras": "2.1.2"
   }
 }