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

     1

#Encoding of BACnet Object Types;;;

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#Code;Object Type;;

     3

0;Analog Input;;

     4

1;Analog Output;;

     5

2;Analog Value;;

     6

3;Binary Input ;;

     7

4;Binary Output;;

     8

5;Binary Value;;

     9

6;Calendar;;

    10

7;Command;;

    11

8;Device;;

    12

9;Event-Enrollment;;

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10;File;;

    14

11;Group;;

    15

12;Loop;;

    16

13;Multistate Input;;

    17

14;Multistate Output

    18

15;Notification Class

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16;Program

    20

17;Schedule

    21

18;Averaging

    22

19;Multistate Value

    23

20;Trend Log

    24

21;Life Safety Point

    25

22;Life Safety Zone

    26

23;Accumulator

    27

24;Pulse Converter