Remove unused import from a test

I forgot to remove this import when I changed this test.

Author: bjorn3

tests/ui/error-codes/E0152-duplicate-lang-items.rs

@@ -8,10 +8,6 @@
 
 #![feature(lang_items)]
 
-extern crate core;
-
-use core::panic::PanicInfo;
-
 #[lang = "eh_personality"]
 fn personality() {
     //~^ ERROR: found duplicate lang item `eh_personality`

tests/ui/error-codes/E0152-duplicate-lang-items.stderr

@@ -1,5 +1,5 @@
 error[E0152]: found duplicate lang item `eh_personality`
-  --> $DIR/E0152-duplicate-lang-items.rs:16:1
+  --> $DIR/E0152-duplicate-lang-items.rs:12:1
    |
 LL | / fn personality() {
 LL | |