Enable remove_storage_markers MIR-opt test

tests/mir-opt/remove_storage_markers.rs

@@ -1,4 +1,3 @@
-// skip-filecheck
 // EMIT_MIR_FOR_EACH_PANIC_STRATEGY
 // unit-test: RemoveStorageMarkers
 
@@ -8,6 +7,10 @@
 
 // EMIT_MIR remove_storage_markers.main.RemoveStorageMarkers.diff
 fn main() {
+    // CHECK-LABLE: fn main(
+
+    // CHECK-NOT: StorageDead
+    // CHECK-NOT: StorageLive
     let mut sum = 0;
     for i in 0..10 {
         sum += i;