Fix 唔 and 冇 in Jyutping

[jiru]

sarefo reported that 冇 is mou5, not mou2, and 唔 is m4, not ng4.

[sarefo]

also, 佢 is commonly keoi5, not heoi5 (only very rarely heard).

[allan-simon]

Hello thanks for the report, don't hesitate to do a pull request, the file to edit is in doc/cantonese.xml , i will merge them in the second.
Otherwise I will try to find the time this weekend to do it , but i don't want to promise anything :/