Update mcr.microsoft.com/azure-functions/dotnet Docker tag to v4 (#1871)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| mcr.microsoft.com/azure-functions/dotnet | final | major | `2.0` ->
`4.0` |

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classic-azure-ts-aks-keda/functionapp/Dockerfile

@@ -5,7 +5,7 @@ RUN cd /src/dotnet-function-app && \
     mkdir -p /home/site/wwwroot && \
     dotnet publish *.csproj --output /home/site/wwwroot
 
-FROM mcr.microsoft.com/azure-functions/dotnet:2.0@sha256:54f16c02b57d2f5721e9a098dbfa4c826f03af478fbe50b68e46d82d594b95c0
+FROM mcr.microsoft.com/azure-functions/dotnet:4.0@sha256:891d44d0685b0a7a829000bcb94f95f6859b5581f0e542f6134e629babede2a8
 ENV AzureWebJobsScriptRoot=/home/site/wwwroot \
     AzureFunctionsJobHost__Logging__Console__IsEnabled=true