[fixup] Tweak test

Author: momchil-velikov

llvm/test/MC/AArch64/SME2p2/fmop4as-fp64-non-widening.s

@@ -6,7 +6,7 @@
 // RUN: llvm-mc -triple=aarch64 -filetype=obj -mattr=+sme2p2,+sme-f64f64 < %s \
 // RUN:        | llvm-objdump -d --mattr=+sme2p2,+sme-f64f64 - | FileCheck %s --check-prefix=CHECK-INST
 // RUN: llvm-mc -triple=aarch64 -filetype=obj -mattr=+sme2p2,+sme-f64f64 < %s \
-// RUN:        | llvm-objdump -d --mattr=-sme2 - | FileCheck %s --check-prefix=CHECK-UNKNOWN
+// RUN:        | llvm-objdump -d --mattr=-sme2p2 - | FileCheck %s --check-prefix=CHECK-UNKNOWN
 // Disassemble encoding and check the re-encoding (-show-encoding) matches.
 // RUN: llvm-mc -triple=aarch64 -show-encoding -mattr=+sme2p2,+sme-f64f64 < %s \
 // RUN:        | sed '/.text/d' | sed 's/.*encoding: //g' \