Bump xunit from 2.5.3 to 2.6.3 (#379)

Bumps [xunit](https://github.com/xunit/xunit) from 2.5.3 to 2.6.3.
- [Commits](xunit/xunit@2.5.3...2.6.3)

---
updated-dependencies:
- dependency-name: xunit
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

src/GraphQLParser.ApiTests/GraphQLParser.ApiTests.csproj

@@ -9,7 +9,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
     <PackageReference Include="Shouldly" Version="4.2.1" />
-    <PackageReference Include="xunit" Version="2.5.3" />
+    <PackageReference Include="xunit" Version="2.6.3" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.5.1" />
     <PackageReference Include="PublicApiGenerator" Version="11.0.0" />
   </ItemGroup>