Apply suggestions from code review

Co-authored-by: Matt Arsenault <[email protected]>

Author: ningxinr

llvm/test/CodeGen/AArch64/GlobalISel/knownbits-sub.mir

@@ -1,5 +1,5 @@
 # NOTE: Assertions have been autogenerated by utils/update_givaluetracking_test_checks.py UTC_ARGS: --version 5
-# RUN: llc -mtriple aarch64 -passes="print<gisel-value-tracking>" %s -o - 2>&1 | FileCheck %s
+# RUN: llc -mtriple=aarch64 -passes='print<gisel-value-tracking>' -filetype=null %s 2>&1 | FileCheck %s
 
 ---
 name:            Cst