Prelease tag should be "if not signingbranch"

Pipelines/Templates/Variables.yaml

@@ -7,7 +7,7 @@ variables:
     UnityVersion: $(Unity2020LTSVer)
     ProductVersion.Patch: $[counter(variables['ProductMajorMinor'], 0)]
     ProductVersion.Tag: 
-    ${{ if eq(variables['Build.SourceBranchName'], variables['SigningBranch']) }}:
+    ${{ if ne(variables['Build.SourceBranchName'], variables['SigningBranch']) }}:
       ProductVersion.Tag: '-prerelease.${Build.SourceBranchName}.$(Build.BuildNumber)'
     ProductVersion: $(ProductMajorMinor).$(ProductVersion.Patch)
     NpmPackageName: 'com.microsoft.spatialaudio.spatializer.unity'