bump docker image to net 5

.drone.yml

@@ -7,18 +7,18 @@
 
     steps:
     - name: test
-      image: mcr.microsoft.com/dotnet/core/sdk:3.1
+      image: docker pull mcr.microsoft.com/dotnet/runtime:5.0
       commands:
         - dotnet build -c Release
         - dotnet test -c Release
 
     - name: deploy
-      image: mcr.microsoft.com/dotnet/core/sdk:3.1
+      image: docker pull mcr.microsoft.com/dotnet/runtime:5.0
       environment:
         API_KEY:
           from_secret: API_KEY
       commands:
-        - dotnet nuget push /build/encompass-cs/bin/Release/EncompassECS.Framework.*.nupkg -s https://api.nuget.org/v3/index.json -k $API_KEY 
+        - dotnet nuget push /build/encompass-cs/bin/Release/EncompassECS.Framework.*.nupkg -s https://api.nuget.org/v3/index.json -k $API_KEY
       when:
         ref:
         - refs/tags/*.*.*