[cleanup] `Ty::is_ref` and `Ty::is_region_ptr` are identical

[scottmcm]

is_ref:

rust/compiler/rustc_middle/src/ty/sty.rs

Lines 1809 to 1811 in da7c50c

	pub fn is_ref(self) -> bool {
	matches!(self.kind(), Ref(..))
	}

is_region_ptr:

rust/compiler/rustc_middle/src/ty/sty.rs

Lines 1917 to 1919 in da7c50c

	pub fn is_region_ptr(self) -> bool {
	matches!(self.kind(), Ref(..))
	}

I don't know which name is better, but there probably shouldn't be two is_* helpers doing exactly the same thing.

[compiler-errors]

I prefer is_ref. We don't really call them "region pointers" anymore.

[mu001999]

@rustbot claim