Exclude pyjslib.py from python3 syntax correction check

pyjs doesn't support python3 and it's unmaintained.
async is a new keyword introduced in python 3.7.

./tests/tools/check_source.sh
Syntax checking using python3 ...
Python 3.7.2+

Syntax error in ./runtime/Worker.py
File "./svgui/pyjs/lib/pyjslib.py", line 24
def import_module(path, parent_module, module_name, dynamic=1, async=False):
^
SyntaxError: invalid syntax

revert occasionally committed changed first_steps project.

project was changed by commit:
update translations from https://www.transifex.com/beremiz/beremiz-ide (756d02cf78db)

Merged in masterschlumpf/beremiz/generate-button (pull request #38)

"Generate Prgram" button

Approved-by: Andrey Skvortsov <andrej.skvortzov@gmail.com>