fix(pwsh): stop paths from being interpreted as patterns (starship#1569)

Convert-Path in the powershell prompt script works with -Path,
which interprets paths as wildcard patterns.  

Not all valid paths are also valid wildcard patterns, possibly causing
the prompt to error (eg []*).  

Replace it with -LiteralPath that makes Convert-Path use the path as-is.

src/init/starship.ps1

@@ -8,7 +8,7 @@ function global:prompt {
     $jobs = @(Get-Job | Where-Object { $_.State -eq 'Running' }).Count
 
     $env:PWD = $PWD
-    $current_directory = (Convert-Path $PWD)
+    $current_directory = (Convert-Path -LiteralPath $PWD)
 
     if ($lastCmd = Get-History -Count 1) {
         $duration = [math]::Round(($lastCmd.EndExecutionTime - $lastCmd.StartExecutionTime).TotalMilliseconds)