[Translator] Do not use cache if debug is on

Q | A
------------- | ------------- | -----
Bug fix? | yes
New feature? | no
BC breaks? | no
Deprecations? | no
Tests pass? | yes
Fixed tickets | #11530 
License | MIT
Doc PR | N/A

As I can't find a way to know if a new translation file have been added to invalidate the cache in the method isFresh of ConfigCache I decided to go with the easy way and never use the cache if the debug is turned on. 

I'm pretty sure that trying to determine if we should use the cache or not is heavier that just not use it.