Remove atom/language-c grammar from objective-c extension

[alexr00]

See #74219 for details.

[alexr00]

I have checked that our test .mm file looks ok, but I don't use Objective-C++ often. @ambershark-mike @Muirey03 if you are interested/willing to sanity check the Objective-C++ syntax highlighting that would be very helpful! I have just brought in the changes that we talked about about here. The insiders build tomorrow will have the changes.

[Muirey03]

Sure, I'll check it out tomorrow then, thank you.

[ambershark-mike]

Thanks @alexr00! I'll try to check it out as well. I don't use obj-c very often either. I try to write more cross platform code (usually C++), but sometimes get stuck in a platform specific language. I know just enough objective-c to be dangerous (and frustrated). 😆

[Muirey03]

I tried it out a bit and everything seemed to be working correctly, thank you. @alexr00