Fixes #29308: Respect VIRTUAL_ENV_DISABLE_PROMPT in Activate.ps1.

Lib/venv/scripts/nt/Activate.ps1

@@ -29,6 +29,7 @@ deactivate -nondestructive
 
 $env:VIRTUAL_ENV="__VENV_DIR__"
 
+if (! $env:VIRTUAL_ENV_DISABLE_PROMPT) {
     # Set the prompt to include the env name
     # Make sure _OLD_VIRTUAL_PROMPT is global
     function global:_OLD_VIRTUAL_PROMPT {""}
@@ -37,6 +38,7 @@ function global:prompt {
         Write-Host -NoNewline -ForegroundColor Green '__VENV_PROMPT__'
         _OLD_VIRTUAL_PROMPT
     }
+}
 
 # Clear PYTHONHOME
 if (Test-Path env:PYTHONHOME) {