Update version tests to use NextReleaseVersion from metadata.json (#9646)

tools/ci.psm1

@@ -421,7 +421,7 @@ function Get-ReleaseTag
 {
     $metaDataPath = Join-Path -Path $PSScriptRoot -ChildPath 'metadata.json'
     $metaData = Get-Content $metaDataPath | ConvertFrom-Json
-    $releaseTag = $metadata.PreviewReleaseTag
+    $releaseTag = $metadata.NextReleaseTag
     if($env:BUILD_BUILID)
     {
         $releaseTag = $releaseTag.split('.')[0..2] -join '.'

tools/metadata.json

@@ -3,5 +3,5 @@
   "PreviewReleaseTag": "v6.2.0-rc.1",
   "ServicingReleaseTag": "v6.1.4",
   "ReleaseTag": "v6.2.1",
-  "NextReleaseTag": "v6.2.0-rc.1"
+  "NextReleaseTag": "v7.0.0-preview.1"
 }