checks: Fix E402 Flake8 in for wxGUI Sphinx doc (#4391)

This fixes Flake8 E402 (Module level import not at top of file) for Sphinx documentation generator configuration script by removing import path manipulation block which was not properly working anyway.

.flake8

@@ -25,7 +25,6 @@ per-file-ignores =
     doc/python/m.distance.py: E501
     doc/gui/wxpython/example/dialogs.py: F401
     gui/scripts/d.wms.py: E501
-    gui/wxpython/docs/wxgui_sphinx/conf.py: E402, W291
     gui/wxpython/gcp/manager.py: E722
     gui/wxpython/gui_core/*: E722
     gui/wxpython/gui_core/dialogs.py: E722

gui/wxpython/docs/wxgui_sphinx/conf.py

@@ -10,21 +10,9 @@
 # All configuration values have a default; values that are commented out
 # serve to show the default.
 
-import sys
-import os
 from datetime import date
 import string
 from shutil import copy
-
-# If extensions (or modules to document with autodoc) are in another directory,
-# add these directories to sys.path here. If the directory is relative to the
-# documentation root, use os.path.abspath to make it absolute, like shown here.
-if not os.getenv("GISBASE"):
-    sys.exit("GISBASE not defined")
-sys.path.insert(
-    0, os.path.abspath(os.path.join(os.environ["GISBASE"], "etc", "python", "grass"))
-)
-
 from grass.script import core
 
 footer_tmpl = string.Template(