Fix spelling and grammar on AI Translate module

Sven Decabooterrequested to merge
issue/ai_translate-3557038:3557038-spelling-and-grammar into 1.3.x

There was a spelling issue noted by Dries for the module description and some other spelling and grammar issues fixed. Also a redundant message appearing on the User Interface Translation form about provider configuration.

Closes #3557038

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