change lowercase function to mb_strtolower instead of strtolower

[enescakir]

?	!
Type	bug
BC Break	no
Fixed issues	#1050

Summary

I am trying to get chat_id in a custom command.

$chatID = $this->getMessage()->getChat()->getId();

But it returns null for chat_id all the time if language is set to Turkish.

I tracked issue and strtolower('getId') returns getId in Turkish instead of getid in Entity class.

mb_strtolower('getId') workings corrects and returns getid.

[noplanman]

Thanks for the patch!

Please add a short message in the CHANGELOG.md too please, in the Unreleased -> Fixed section too, then I can merge this 👍

[enescakir]

PTAL @noplanman 👀

[noplanman]

Thanks @enescakir 🎉