Bump Azure.Messaging.EventGrid from 4.18.0 to 4.20.0

Bumps [Azure.Messaging.EventGrid](https://github.com/Azure/azure-sdk-for-net) from 4.18.0 to 4.20.0.
- [Release notes](https://github.com/Azure/azure-sdk-for-net/releases)
- [Commits](Azure/azure-sdk-for-net@Azure.Messaging.EventGrid_4.18.0...Azure.Messaging.EventGrid_4.20.0)

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

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

src/MediatR.Azure.EventGrid.Serialization/MediatR.Azure.EventGrid.Serialization.csproj

@@ -38,7 +38,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Azure.Messaging.EventGrid" Version="4.18.0" />
+    <PackageReference Include="Azure.Messaging.EventGrid" Version="4.20.0" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="All" />
     <PackageReference Include="MinVer" Version="4.3.0" PrivateAssets="All" />
     <PackageReference Include="SonarAnalyzer.CSharp" Version="9.10.0.77988">