Update Dockerfile inline with requirments script changes (#387)

* Use dotnet sdk 6.0 to match requirements of 3e17453

* Use python 3 to match requirements of 07a3903

Dockerfile

@@ -48,13 +48,13 @@ RUN apt install -y software-properties-common
 RUN add-apt-repository universe -y
 RUN apt install -y apt-transport-https
 RUN apt update -y
-RUN apt install -y dotnet-sdk-3.1
+RUN apt install -y dotnet-sdk-6.0
 
 # Required for "with-go" profile
 RUN apt install -y golang
 
 # Required for "with-python" profile
-RUN apt install -y python-setuptools python
+RUN apt install -y python-setuptools python3 python-is-python3
 
 # Required for running on Windows systems
 RUN apt install -y dos2unix