Bump Nerdbank.GitVersioning from 3.8.38-alpha to 3.9.50

---
updated-dependencies:
- dependency-name: Nerdbank.GitVersioning
  dependency-version: 3.9.50
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

Directory.Build.props

@@ -2,7 +2,7 @@
   <!-- Shared package refs -->
   <ItemGroup>
     <!-- NBGV drives versions; PrivateAssets=all keeps it out of consumers -->
-    <PackageReference Include="Nerdbank.GitVersioning" Version="3.8.38-alpha" PrivateAssets="all" />
+    <PackageReference Include="Nerdbank.GitVersioning" Version="3.9.50" PrivateAssets="all" />
 
     <!-- SourceLink for GitHub -->
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0">