Update ui tests

Author: oli-obk

src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.rs

@@ -52,7 +52,7 @@
 //~^ WARN unused attribute
 #![path = "3800"] //~ WARN unused attribute
 #![automatically_derived] //~ WARN unused attribute
-#![no_mangle] //~ WARN unused attribute
+#![no_mangle]
 #![no_link] //~ WARN unused attribute
 // see issue-43106-gating-of-derive.rs
 #![should_panic] //~ WARN unused attribute

src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr

@@ -1152,12 +1152,6 @@ warning: unused attribute
 LL | #![automatically_derived]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^
 
-warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:55:1
-   |
-LL | #![no_mangle]
-   | ^^^^^^^^^^^^^
-
 warning: unused attribute
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:56:1
    |