fixup! Remove unused check prefix

Author: topperc

llvm/test/CodeGen/RISCV/GlobalISel/legalizer/legalize-abs-diff-rv64.mir

@@ -1,8 +1,8 @@
 # NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
 # RUN: llc -mtriple=riscv64 -run-pass=legalizer %s -o - \
-# RUN:   | FileCheck %s --check-prefixes=CHECK,RV64I
+# RUN:   | FileCheck %s --check-prefixes=RV64I
 # RUN: llc -mtriple=riscv64 -mattr=+zbb -run-pass=legalizer %s -o - \
-# RUN:   | FileCheck %s --check-prefixes=CHECK,RV64ZBB
+# RUN:   | FileCheck %s --check-prefixes=RV64ZBB
 
 ---
 name:            abds_i8