Use new MyGet source for packages and symbols

Author: JimBobSquarePants

.github/workflows/build-and-test.yml

@@ -144,7 +144,7 @@ jobs:
             - name: MyGet Publish
               shell: pwsh
               run: |
-                  $source = "https://www.myget.org/F/sixlabors/api/v2/package"
-                  $symbolSource = "https://www.myget.org/F/sixlabors/api/v3/index.json"
-                  dotnet nuget push .\artifacts\*.nupkg -k ${{secrets.MYGET_TOKEN}} -sk ${{secrets.MYGET_TOKEN}} -s $source -ss $symbolSource
+                  $key = ${{secrets.MYGET_TOKEN}}
+                  $source = "https://www.myget.org/F/sixlabors/api/v3/index.json"
+                  dotnet nuget push .\artifacts\*.nupkg -k $key -sk $key -s $source -ss $source
               # TODO: If github.ref starts with 'refs/tags' then it was tag push and we can optionally push out package to nuget.org