[BOLT][AArch64] Fix adr-relaxation.s test (#143151)

On some AArch64 machines the splitting was inconsistent.
This causes cold `foo` to have a `mov` instruction before adrp.
    
```
<foo.cold.0>:
  mov     x0, #0x0                // =0
  adrp    x1, 0x600000 <_start>
  add     x1, x1, #0x14
  ret
```
    
This patch removes the `mov` instruction right above .L2, making
splitting deterministic.

bolt/test/AArch64/adr-relaxation.s

@@ -34,7 +34,6 @@ foo:
   .cfi_startproc
   cmp  x1, x11
   b.hi  .L2
-  mov  x0, #0x0
 .L2:
 # CHECK-FOO: <foo.cold.0>:
 # CHECK-FOO-NEXT: adrp