Remove extension of the sys.path (aka PYTHONPATH). Running instance directly
from repository's folder is a relict from the early beginning in
2014 (fd651083f) and is no longer supported.
Since commit dd46629 was merged the command line 'searx-run' exists and should
be used.
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>