Remove some errors in UI tests

As we now need to run THIR unsafeck before MIR build, errors in unsafeck can cause the compilation to be aborted earlier.

src/test/ui/async-await/async-unsafe-fn-call-in-safe.rs

@@ -16,6 +16,6 @@ async fn g() {
 }
 
 fn main() {
-    S::f(); //~ ERROR call to unsafe function is unsafe
-    f(); //~ ERROR call to unsafe function is unsafe
+    S::f(); //[mir]~ ERROR call to unsafe function is unsafe
+    f(); //[mir]~ ERROR call to unsafe function is unsafe
 }

src/test/ui/async-await/async-unsafe-fn-call-in-safe.thir.stderr

@@ -14,22 +14,6 @@ LL |     f();
    |
    = note: consult the function's documentation for information on how to avoid undefined behavior
 
-error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
-  --> $DIR/async-unsafe-fn-call-in-safe.rs:19:5
-   |
-LL |     S::f();
-   |     ^^^^^^ call to unsafe function
-   |
-   = note: consult the function's documentation for information on how to avoid undefined behavior
-
-error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
-  --> $DIR/async-unsafe-fn-call-in-safe.rs:20:5
-   |
-LL |     f();
-   |     ^^^ call to unsafe function
-   |
-   = note: consult the function's documentation for information on how to avoid undefined behavior
-
-error: aborting due to 4 previous errors
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0133`.

src/test/ui/consts/const-extern-fn/const-extern-fn-requires-unsafe.rs

@@ -9,5 +9,5 @@ fn main() {
     let a: [u8; foo()];
     //~^ ERROR call to unsafe function is unsafe and requires unsafe function or block
     foo();
-    //~^ ERROR call to unsafe function is unsafe and requires unsafe function or block
+    //[mir]~^ ERROR call to unsafe function is unsafe and requires unsafe function or block
 }

src/test/ui/consts/const-extern-fn/const-extern-fn-requires-unsafe.thir.stderr

@@ -1,11 +1,3 @@
-error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
-  --> $DIR/const-extern-fn-requires-unsafe.rs:11:5
-   |
-LL |     foo();
-   |     ^^^^^ call to unsafe function
-   |
-   = note: consult the function's documentation for information on how to avoid undefined behavior
-
 error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
   --> $DIR/const-extern-fn-requires-unsafe.rs:9:17
    |
@@ -14,6 +6,6 @@ LL |     let a: [u8; foo()];
    |
    = note: consult the function's documentation for information on how to avoid undefined behavior
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0133`.