[TypeSpec Validation] Remove duplicate error messages in Get-TypeSpec-Folders.ps1 (#25846)

- Continuation of #25841

Author: ckairen

eng/scripts/Get-TypeSpec-Folders.ps1

@@ -49,17 +49,22 @@ else {
 }
 
 $typespecFolders = @()
+$skippedTypespecFolders = @()
 foreach ($file in $changedFiles) {
   if ($file -match 'specification\/[^\/]*\/') {
     if (Test-Path $matches[0]) {
       $typespecFolder = (Get-ChildItem -path $matches[0] tspconfig.* -Recurse).Directory.FullName | ForEach-Object {if ($_) { [IO.Path]::GetRelativePath($($pwd.path), $_) }}
       $typespecFolders += $typespecFolder -replace '\\', '/'
     } else {
-      Write-Host "Cannot find directory $($matches[0])"
+      $skippedTypespecFolders += $matches[0]
     }
   }
 }
 
+foreach ($skippedTypespecFolder in $skippedTypespecFolders | Select-Object -Unique) {
+  Write-Host "Cannot find directory $skippedTypespecFolder"
+}
+
 $typespecFolders = $typespecFolders | Select-Object -Unique | Sort-Object
 
 return $typespecFolders