DefaultArgParser.py: Update coala help
DefaultArgParser.py: Update coala help

Replace "--filter-by-language" with "--filter-by language"
in coala CLI help string because "--filter-by-language" is
deprecated.

Closes https://github.com/coala/coala/issues/4652

coala/coala,jayvdb/coala,coala/coala,shreyans800755/coala,nemaniarjun/coala,karansingh1559/coala,nemaniarjun/coala,coala-analyzer/coala,Nosferatul/coala,coala-analyzer/coala,SanketDG/coala,SanketDG/coala,CruiseDevice/coala,jayvdb/coala,karansingh1559/coala,karansingh1559/coala,aptrishu/coala,CruiseDevice/coala,Nosferatul/coala,coala/coala,shreyans800755/coala,shreyans800755/coala,coala-analyzer/coala,aptrishu/coala,aptrishu/coala,nemaniarjun/coala,Nosferatul/coala,CruiseDevice/coala,jayvdb/coala,SanketDG/coala