doc: Ignore F401 in dialogs.py (#4488)

dialogs.py has an instance of F401 error for unused import of grass library. However as mentioned in the comment and post discussion with @wenzeslaus I decided it would be better to ignore this error for now in case it breaks any underlying dependencies regarding gettext.install()

.flake8

@@ -22,7 +22,6 @@ per-file-ignores =
     __init__.py: F401, F403
     man/build_html.py: E501
     doc/python/m.distance.py: E501
-    doc/gui/wxpython/example/dialogs.py: F401
     gui/scripts/d.wms.py: E501
     gui/wxpython/image2target/*: F841, E722
     gui/wxpython/image2target/g.gui.image2target.py: E501, F841

doc/gui/wxpython/example/dialogs.py

@@ -20,7 +20,7 @@
 # So we need to import it before any of the GUI code.
 # NOTE: in this particular case, we don't really need the grass library;
 # NOTE: we import it just for the side effects of gettext.install()
-import grass
+import grass  # noqa: F401
 
 from core import globalvar
 from gui_core.dialogs import SimpleDialog