Bump Microsoft.Identity.Web.GraphServiceClient in /GraphTutorial

Bumps [Microsoft.Identity.Web.GraphServiceClient](https://github.com/AzureAD/microsoft-identity-web) from 2.19.1 to 2.20.0.
- [Release notes](https://github.com/AzureAD/microsoft-identity-web/releases)
- [Changelog](https://github.com/AzureAD/microsoft-identity-web/blob/2.20.0/changelog.md)
- [Commits](https://github.com/AzureAD/microsoft-identity-web/commits/2.20.0)

---
updated-dependencies:
- dependency-name: Microsoft.Identity.Web.GraphServiceClient
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

GraphTutorial/GraphTutorial.csproj

@@ -14,7 +14,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.Identity.Web" Version="2.19.1" />
-    <PackageReference Include="Microsoft.Identity.Web.GraphServiceClient" Version="2.19.1" />
+    <PackageReference Include="Microsoft.Identity.Web.GraphServiceClient" Version="2.20.0" />
     <PackageReference Include="Microsoft.Identity.Web.UI" Version="2.19.1" />
     <PackageReference Include="Stylecop.Analyzers" Version="1.2.0-beta.556">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>