Bump NUnit3TestAdapter from 3.14.0 to 3.15.0

Bumps [NUnit3TestAdapter](https://github.com/nunit/nunit3-vs-adapter) from 3.14.0 to 3.15.0.
- [Release notes](https://github.com/nunit/nunit3-vs-adapter/releases)
- [Commits](nunit/nunit3-vs-adapter@V3.14...V3.15)

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

Author: dependabot-preview[bot]

System.IO.Abstractions.TestingHelpers.Tests/System.IO.Abstractions.TestingHelpers.Tests.csproj

@@ -47,7 +47,7 @@
 
   <ItemGroup>
     <PackageReference Include="nunit" Version="3.12.0" />
-    <PackageReference Include="NUnit3TestAdapter" Version="3.14.0" />
+    <PackageReference Include="NUnit3TestAdapter" Version="3.15.0" />
   </ItemGroup>
 
   <ItemGroup>