Update tests.

Author: m-ou-se

tests/ui/lint/cli-lint-override.forbid_warn.stderr

@@ -2,9 +2,8 @@ error: extern declarations without an explicit ABI are deprecated
   --> $DIR/cli-lint-override.rs:12:1
    |
 LL | extern fn foo() {}
-   | ^^^^^^^^^^^^^^^ ABI should be specified here
+   | ^^^^^^ help: explicitly specify the C ABI: `extern "C"`
    |
-   = help: the default ABI is C
    = note: requested on the command line with `-F missing-abi`
 
 error: aborting due to 1 previous error

tests/ui/lint/cli-lint-override.force_warn_deny.stderr

@@ -2,9 +2,8 @@ warning: extern declarations without an explicit ABI are deprecated
   --> $DIR/cli-lint-override.rs:12:1
    |
 LL | extern fn foo() {}
-   | ^^^^^^^^^^^^^^^ ABI should be specified here
+   | ^^^^^^ help: explicitly specify the C ABI: `extern "C"`
    |
-   = help: the default ABI is C
    = note: requested on the command line with `--force-warn missing-abi`
 
 warning: 1 warning emitted

tests/ui/lint/cli-lint-override.warn_deny.stderr

@@ -2,9 +2,8 @@ error: extern declarations without an explicit ABI are deprecated
   --> $DIR/cli-lint-override.rs:12:1
    |
 LL | extern fn foo() {}
-   | ^^^^^^^^^^^^^^^ ABI should be specified here
+   | ^^^^^^ help: explicitly specify the C ABI: `extern "C"`
    |
-   = help: the default ABI is C
    = note: requested on the command line with `-D missing-abi`
 
 error: aborting due to 1 previous error

tests/ui/unpretty/expanded-exhaustive.rs

@@ -452,15 +452,15 @@ mod items {
     /// ItemKind::Fn
     mod item_fn {
         pub const unsafe extern "C" fn f() {}
-        pub async unsafe extern fn g() {}
+        pub async unsafe extern "C" fn g() {}
         fn h<'a, T>() where T: 'a {}
 
         trait TraitItems {
-            unsafe extern fn f();
+            unsafe extern "C" fn f();
         }
 
         impl TraitItems for _ {
-            default unsafe extern fn f() {}
+            default unsafe extern "C" fn f() {}
         }
     }
 
@@ -472,7 +472,7 @@ mod items {
     /// ItemKind::ForeignMod
     mod item_foreign_mod {
         unsafe extern "C++" {}
-        unsafe extern {}
+        unsafe extern "C" {}
     }
 
     /// ItemKind::GlobalAsm

tests/ui/unpretty/expanded-exhaustive.stdout

@@ -433,21 +433,21 @@ mod items {
     /// ItemKind::Fn
     mod item_fn {
         pub const unsafe extern "C" fn f() {}
-        pub async unsafe extern fn g() {}
+        pub async unsafe extern "C" fn g() {}
         fn h<'a, T>() where T: 'a {}
         trait TraitItems {
-            unsafe extern fn f();
+            unsafe extern "C" fn f();
         }
         impl TraitItems for _ {
-            default unsafe extern fn f() {}
+            default unsafe extern "C" fn f() {}
         }
     }
     /// ItemKind::Mod
     mod item_mod { }
     /// ItemKind::ForeignMod
     mod item_foreign_mod {
         unsafe extern "C++" {}
-        unsafe extern {}
+        unsafe extern "C" {}
     }
     /// ItemKind::GlobalAsm
     mod item_global_asm {