build(deps): bump xunit from 2.6.1 to 2.6.3 (#2834)

* build(deps): bump xunit from 2.6.1 to 2.6.3

Bumps [xunit](https://github.com/xunit/xunit) from 2.6.1 to 2.6.3.
- [Commits](https://github.com/xunit/xunit/compare/2.6.1...2.6.3)

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

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

* Add required async/awaits

* public async void --> public async Task

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Keegan Campbell <me@kfcampbell.com>

Octokit.Tests/Caching/CachingHttpClientTests.cs

@@ -20,7 +20,7 @@ namespace Octokit.Tests.Caching
         public class TheSendMethod
         {
             [Fact]
-            public void EnsuresNonNullArguments()
+            public async Task EnsuresNonNullArguments()
             {
                 // arrange
                 var underlyingClient = Substitute.For<IHttpClient>();
@@ -29,7 +29,7 @@ namespace Octokit.Tests.Caching
                 var cachingHttpClient = new CachingHttpClient(underlyingClient, responseCache);
 
                 // act + assert
-                Assert.ThrowsAsync<ArgumentNullException>(() => cachingHttpClient.Send(null, CancellationToken.None));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => cachingHttpClient.Send(null, CancellationToken.None));
             }
 
             [Theory]