improve readability of SPACE_BEFORE_FUNC error message

[MoulatiMehdi]

I have been using the norminette in the piscine, and the SPACE_BEFORE_FUNC error message was a little hard to understand.
it confuses me a lot of times whether "I should use the space" or "the space is what is causing the problem".

Change :

Before : space before function name
After : Found space when expecting tab before function name

Note :

I apply the changes to the testing files as well.

Thanks for your time.