Improve the code quality by using matches macro

compiler/rustc_middle/src/ty/sty.rs

@@ -1628,17 +1628,11 @@ impl RegionKind {
     }
 
     pub fn is_late_bound(&self) -> bool {
-        match *self {
-            ty::ReLateBound(..) => true,
-            _ => false,
-        }
+        matches!(*self, ty::ReLateBound(..))
     }
 
     pub fn is_placeholder(&self) -> bool {
-        match *self {
-            ty::RePlaceholder(..) => true,
-            _ => false,
-        }
+        matches!(*self, ty::RePlaceholder(..))
     }
 
     pub fn bound_at_or_above_binder(&self, index: DebruijnIndex) -> bool {