Don't remove sys.path entries that come from PYTHONPATH, or else the app cannot
be used in Nixpkgs.

Author: Bjørn Forsman <bjorn.forsman@gmail.com>
diff -uNr spyder-5.4.0.orig/spyder/app/start.py spyder-5.4.0/spyder/app/start.py
--- spyder-5.4.0.orig/spyder/app/start.py	2022-08-30 02:02:28.000000000 +0200
+++ spyder-5.4.0/spyder/app/start.py	2023-01-02 11:38:28.138744879 +0100
@@ -6,16 +6,8 @@
 # (see spyder/__init__.py for details)
 # -----------------------------------------------------------------------------
 
-# Remove PYTHONPATH paths from sys.path before other imports to protect against
-# shadowed standard libraries.
 import os
 import sys
-if os.environ.get('PYTHONPATH'):
-    for path in os.environ['PYTHONPATH'].split(os.pathsep):
-        try:
-            sys.path.remove(path.rstrip(os.sep))
-        except ValueError:
-            pass
 
 # Standard library imports
 import ctypes