upgrade pester version to 4.4.4

Author: JamesWTruher

Diff for: tools/appveyor.psm1

@@ -5,7 +5,7 @@ $ErrorActionPreference = 'Stop'
 
 # Implements the AppVeyor 'install' step and installs the required versions of Pester, platyPS and the .Net Core SDK if needed.
 function Invoke-AppVeyorInstall {
-    $requiredPesterVersion = '4.4.1'
+    $requiredPesterVersion = '4.4.4'
     $pester = Get-Module Pester -ListAvailable | Where-Object { $_.Version -eq $requiredPesterVersion }
     if ($null -eq $pester) {
         if ($null -eq (Get-Module -ListAvailable PowershellGet)) {