Online help: Avoid pydev warning under all circumstances

This can also happen when Spyder is installed in a Python 3.11
environment besides our installer.

spyder/plugins/onlinehelp/widgets.py

@@ -23,7 +23,6 @@
 # Local imports
 from spyder.api.translations import _
 from spyder.api.widgets.main_widget import PluginMainWidget
-from spyder.config.base import is_pynsist
 from spyder.plugins.onlinehelp.pydoc_patch import _start_server, _url_handler
 from spyder.widgets.browser import FrameWebView, WebViewActions
 from spyder.widgets.comboboxes import UrlComboBox
@@ -69,10 +68,9 @@ def spyder_safeimport(path, forceload=0, cache={}):
 except Exception:
     pass
 
-# Needed to prevent showing a warning message regarding debugging
-# See spyder-ide/spyder#20390
-if is_pynsist():
-    os.environ["PYDEVD_DISABLE_FILE_VALIDATION"] = "1"
+# Needed to prevent showing a warning message regarding debugging.
+# Fixes spyder-ide/spyder#20390 and spyder-ide/spyder#21171
+os.environ["PYDEVD_DISABLE_FILE_VALIDATION"] = "1"
 
 
 class PydocServer(QThread):