Bump Azure.Identity from 1.20.0 to 1.21.0

---
updated-dependencies:
- dependency-name: Azure.Identity
  dependency-version: 1.21.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

user-auth/GraphTutorial/GraphTutorial.csproj

@@ -21,7 +21,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Azure.Identity" Version="1.20.0" />
+    <PackageReference Include="Azure.Identity" Version="1.21.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="10.0.3" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="10.0.3" />
     <PackageReference Include="Microsoft.Extensions.Configuration.UserSecrets" Version="10.0.3" />