Merged PR 38901: Remove isOutput on variable being set and update publishPath var reference

Remove isOutput on variable being set and update publishPath var reference

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#### AI description  (iteration 1)
#### PR Classification
This pull request is a pipeline fix and code cleanup, adjusting variable setting and reference for improved consistency.

#### PR Summary
The changes remove the "isOutput=true" flag when setting the "publishPath" variable and update the file copy step to correctly reference the "publishPath".
- `/.pipelines/PSResourceGet-Official.yml`: Removed the "isOutput=true" from the variable setting command.
- `/.pipelines/PSResourceGet-Official.yml`: Updated the file copy task to use `publishPath` instead of `signOutPath` for selecting the published package.
<!-- GitOpsUserAgent=GitOps.Apps.Server.pullrequestcopilot -->

Author: Anam Navied

.pipelines/PSResourceGet-Official.yml

@@ -240,7 +240,7 @@ extends:
 
             Register-PSResourceRepository -Name 'localRepo' -Uri $publishPath
             Publish-PSResource -Path "$(signOutPath)\Microsoft.PowerShell.PSResourceGet" -Repository 'localRepo' -Verbose
-            Write-Output "##vso[task.setvariable variable=publishPath;isOutput=true]$publishPath"
+            Write-Output "##vso[task.setvariable variable=publishPath]$publishPath"
           displayName: Create nupkg for publishing
 
         - pwsh: |
@@ -266,7 +266,7 @@ extends:
         - task: CopyFiles@2
           displayName: "Copy nupkg to ob_outputDirectory - '$(ob_outputDirectory)'"
           inputs:
-            Contents: $(signOutPath)\PublishedNupkg\Microsoft.PowerShell.PSResourceGet.*.nupkg
+            Contents: $(publishPath)\Microsoft.PowerShell.PSResourceGet.*.nupkg
             TargetFolder: $(ob_outputDirectory)
 
         - pwsh: |