Bump System.Linq.Async from 6.0.3 to 7.0.0

---
updated-dependencies:
- dependency-name: System.Linq.Async
  dependency-version: 7.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

FirebaseAdmin/FirebaseAdmin.Tests/FirebaseAdmin.Tests.csproj

@@ -18,7 +18,7 @@
     <PackageReference Include="Google.Apis.Auth" Version="1.73.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.13.0" />
     <PackageReference Include="System.Collections.Immutable" Version="8.0.0" />
-    <PackageReference Include="System.Linq.Async" Version="6.0.3" />
+    <PackageReference Include="System.Linq.Async" Version="7.0.0" />
     <PackageReference Include="xunit" Version="2.9.3" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2">
       <PrivateAssets>all</PrivateAssets>