Remove SupportsShouldProcess from Start-PSBootstrap in build.psm1 (#15491)

build.psm1

@@ -1804,9 +1804,7 @@ function Get-RedHatPackageManager {
 }
 
 function Start-PSBootstrap {
-    [CmdletBinding(
-        SupportsShouldProcess=$true,
-        ConfirmImpact="High")]
+    [CmdletBinding()]
     param(
         [string]$Channel = $dotnetCLIChannel,
         # we currently pin dotnet-cli version, and will

tools/ci.psm1

@@ -171,7 +171,7 @@ function Invoke-CIInstall
     }
 
     Set-BuildVariable -Name TestPassed -Value False
-    Start-PSBootstrap -Confirm:$false
+    Start-PSBootstrap
 }
 
 function Invoke-CIxUnit