[llvm] [AMDGPU][test] fix the error case in update_mc_test_check script (PR #112731)

[Ivan Kosarev via llvm-commits]

================
@@ -15,15 +15,14 @@
 
 mc_LIKE_TOOLS = [
     "llvm-mc",
-    "not llvm-mc",
 ]
----------------
kosarev wrote:

Then please add a comment similar to the one we have for llc:
```
# llc is the only llc-like in the LLVM tree but downstream forks can add
# additional ones here if they have them.
```

It would also be nice to fix the name to be all-capitals (probably with a separate patch).

https://github.com/llvm/llvm-project/pull/112731