Run filecheck on dest-prop/dead_stores_better.rs

Author: CastilloDel

tests/mir-opt/dest-prop/dead_stores_better.rs

@@ -1,4 +1,3 @@
-// skip-filecheck
 // EMIT_MIR_FOR_EACH_PANIC_STRATEGY
 // This is a copy of the `dead_stores_79191` test, except that we turn on DSE. This demonstrates
 // that that pass enables this one to do more optimizations.
@@ -12,6 +11,8 @@ fn id<T>(x: T) -> T {
 
 // EMIT_MIR dead_stores_better.f.DestinationPropagation.after.mir
 pub fn f(mut a: usize) -> usize {
+    // CHECK-LABEL: fn f
+    // CHECK: {{_.*}} = {{_.*}}
     let b = a;
     a = 5;
     a = b;