Update a test's diagnostics

Author: oli-obk

src/test/ui/issues/issue-37550.rs

@@ -8,15 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(const_fn)]
-
 const fn x() {
     let t = true;
-    //~^ ERROR let bindings in constant functions are unstable
-    //~| ERROR statements in constant functions are unstable
-    let x = || t;
-    //~^ ERROR let bindings in constant functions are unstable
-    //~| ERROR statements in constant functions are unstable
+    let x = || t; //~ ERROR function pointers in const fn are unstable
 }
 
 fn main() {}

src/test/ui/issues/issue-37550.stderr

@@ -1,35 +1,8 @@
-error[E0658]: let bindings in constant functions are unstable (see issue #48821)
-  --> $DIR/issue-37550.rs:14:13
+error: function pointers in const fn are unstable
+  --> $DIR/issue-37550.rs:13:9
    |
-LL |     let t = true;
-   |             ^^^^
-   |
-   = help: add #![feature(const_let)] to the crate attributes to enable
-
-error[E0658]: statements in constant functions are unstable (see issue #48821)
-  --> $DIR/issue-37550.rs:14:13
-   |
-LL |     let t = true;
-   |             ^^^^
-   |
-   = help: add #![feature(const_let)] to the crate attributes to enable
-
-error[E0658]: let bindings in constant functions are unstable (see issue #48821)
-  --> $DIR/issue-37550.rs:17:13
-   |
-LL |     let x = || t;
-   |             ^^^^
-   |
-   = help: add #![feature(const_let)] to the crate attributes to enable
-
-error[E0658]: statements in constant functions are unstable (see issue #48821)
-  --> $DIR/issue-37550.rs:17:13
-   |
-LL |     let x = || t;
-   |             ^^^^
-   |
-   = help: add #![feature(const_let)] to the crate attributes to enable
+LL |     let x = || t; //~ ERROR function pointers in const fn are unstable
+   |         ^
 
-error: aborting due to 4 previous errors
+error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0658`.