[NFC] Fix test comment formatting

This addresses feedback on PR llvm#152531 which I missed before merging.

../llvm/test/tools/llvm-objdump/DXContainer/input-output-signatures.yaml

Author: llvm-beanz

llvm/test/tools/llvm-objdump/DXContainer/input-output-signatures.yaml

@@ -1,10 +1,10 @@
 # RUN: yaml2obj %s -o %t
 # RUN: llvm-objdump -p %t | FileCheck %s --match-full-lines --strict-whitespace
 
-# This test covers llvm-objdump printing private headers for the ISG1, OSG1, and
-# PSG1 "parts" of the DX container file format. The test uses a few absurdly
-# large values and long string names to ensure that the columns in the printed
-# table widen correctly.
+## This test covers llvm-objdump printing private headers for the ISG1, OSG1,
+## and PSG1 "parts" of the DX container file format. The test uses a few
+## absurdly large values and long string names to ensure that the columns in the
+## printed table widen correctly.
 
 --- !dxcontainer
 Header: