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]

src/Foundatio.AzureServiceBus/Foundatio.AzureServiceBus.csproj

@@ -2,7 +2,7 @@
   <Import Project="..\..\build\common.props" />
   <ItemGroup>
     <PackageReference Include="Azure.Messaging.ServiceBus" Version="7.20.1" />
-    <PackageReference Include="Azure.Identity" Version="1.20.0" />
+    <PackageReference Include="Azure.Identity" Version="1.21.0" />
 
     <PackageReference Include="Foundatio" Version="13.0.0-beta4" Condition="'$(ReferenceFoundatioSource)' == '' OR '$(ReferenceFoundatioSource)' == 'false'" />
     <ProjectReference Include="..\..\..\Foundatio\src\Foundatio\Foundatio.csproj" Condition="'$(ReferenceFoundatioSource)' == 'true'" />