get_user_by_email should be using GET not POST

[towolf]

Same thing only different, the get_user_by_email method should be using GET on the endpoint, see here:

https://api.mattermost.com/#tag/users%2Fpaths%2F~1users~1email~1%7Bemail%7D%2Fget

[Vaelor]

Will be fixed ASAP, but I am not at home until tomorrow evening! Sorry!