Bump Microsoft.NET.StringTools from 18.6.3 to 18.7.1 (#257)

---
updated-dependencies:
- dependency-name: Microsoft.NET.StringTools
  dependency-version: 18.7.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]

Directory.Packages.props

@@ -8,7 +8,7 @@
     <PackageVersion Include="Microsoft.Build.Locator" Version="1.11.2" />
     <PackageVersion Include="Microsoft.Build.Tasks.Core" Version="18.3.3" />
     <PackageVersion Include="Microsoft.Build.Utilities.Core" Version="18.3.3" />
-    <PackageVersion Include="Microsoft.NET.StringTools" Version="18.6.3" />
+    <PackageVersion Include="Microsoft.NET.StringTools" Version="18.7.1" />
     <PackageVersion Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="5.0.0" />
     <PackageVersion Include="Microsoft.CodeAnalysis.Workspaces.MSBuild" Version="5.0.0" />
     <PackageVersion Include="Microsoft.Extensions.DependencyInjection" Version="10.0.9" />