fix some typos in !-related test comments

Author: WaffleLapkin

tests/mir-opt/uninhabited_not_read.rs

@@ -1,7 +1,7 @@
 // skip-filecheck
 
 //@ edition: 2021
-// In ed 2021 and below, we don't fallback `!` to `()`.
+// In ed 2021 and below, we fallback `!` to `()`.
 // This would introduce a `! -> ()` coercion which would
 // be UB if we didn't disallow this explicitly.
 

tests/ui/consts/const-eval/raw-bytes.rs

@@ -34,7 +34,7 @@ const BAD_ENUM2: Enum2 = unsafe { mem::transmute(0usize) };
 #[derive(Copy, Clone)]
 enum Never {}
 
-// An enum with 3 variants of which some are uninhabited -- so the uninhabited variants *do*
+// An enum with 4 variants of which only some are uninhabited -- so the uninhabited variants *do*
 // have a discriminant.
 enum UninhDiscriminant {
     A,