Remove unnecessary `EMIT_MIR_FOR_EACH_BITWIDTH

Author: JakobDegen

src/test/mir-opt/array-index-is-temporary.rs

@@ -7,7 +7,7 @@ unsafe fn foo(z: *mut usize) -> u32 {
     99
 }
 
-// EMIT_MIR_FOR_EACH_BIT_WIDTH
+
 // EMIT_MIR array_index_is_temporary.main.SimplifyCfg-elaborate-drops.after.mir
 fn main() {
     let mut x = [42, 43, 44];