[tests] remove botirc.py from coverage
[tests] remove botirc.py from coverage

botirc.py is deprecated and there are no tests to verify the code.
Remove this file from codecov.

Change-Id: Icda56658551f763556e7a63124bfcfabdce13891

wikimedia/pywikibot-core,PersianWikipedia/pywikibot-core,wikimedia/pywikibot-core