Bump Azure.Identity from 1.5.0 to 1.6.0

Bumps [Azure.Identity](https://github.com/Azure/azure-sdk-for-net) from 1.5.0 to 1.6.0.
- [Release notes](https://github.com/Azure/azure-sdk-for-net/releases)
- [Commits](Azure/azure-sdk-for-net@Azure.Identity_1.5.0...Azure.Identity_1.6.0)

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

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

Author: dependabot[bot]

src/FluentEmail.Graph/FluentEmail.Graph.csproj

@@ -36,7 +36,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Azure.Identity" Version="1.5.0" />
+    <PackageReference Include="Azure.Identity" Version="1.6.0" />
     <PackageReference Include="FluentEmail.Core" Version="3.0.2" />
     <PackageReference Include="JetBrains.Annotations" Version="2021.3.0">
       <PrivateAssets>all</PrivateAssets>