Remove useless -O2 from test

Author: rovka

llvm/test/CodeGen/AMDGPU/release-vgprs-gfx12.mir

@@ -1,5 +1,5 @@
-# RUN: llc -O2 -march=amdgcn -mcpu=gfx1200 -run-pass=si-insert-waitcnts -verify-machineinstrs -o - %s | FileCheck %s -check-prefixes=CHECK,DEFAULT
-# RUN: llc -O2 -march=amdgcn -mcpu=gfx1200 -mattr=+dynamic-vgpr -run-pass=si-insert-waitcnts -verify-machineinstrs -o - %s | FileCheck %s -check-prefixes=CHECK,DVGPR
+# RUN: llc -march=amdgcn -mcpu=gfx1200 -run-pass=si-insert-waitcnts -verify-machineinstrs -o - %s | FileCheck %s -check-prefixes=CHECK,DEFAULT
+# RUN: llc -march=amdgcn -mcpu=gfx1200 -mattr=+dynamic-vgpr -run-pass=si-insert-waitcnts -verify-machineinstrs -o - %s | FileCheck %s -check-prefixes=CHECK,DVGPR
 
 --- |
   define amdgpu_ps void @tbuffer_store1() { ret void }