Merge pull request #4859 from Ullmie02/ci

Don't build unstable Nuget packages on tags

(cherry picked from commit 7227d0d48bbfd9a781e52727490c59d6eb8157ba)
Signed-off-by: Joshua M. Boniface <joshua@boniface.me>

.ci/azure-pipelines-package.yml

@@ -210,6 +210,7 @@ jobs:
 
   - task: DotNetCoreCLI@2
     displayName: 'Build Unstable Nuget packages'
+    condition: startsWith(variables['Build.SourceBranch'], 'refs/heads/master')
     inputs:
       command: 'custom'
       projects: |