DebugInfo: Fix test to match comment

This produced a few verifier warnings that came up while I was
investigating something else here. Change the assembly to match the
comment so it's warning free. Doesn't seem necessary to change the
CHECKs for the test since it's just a bug in the test, not in the code
under test.

Author: dwblaikie

llvm/test/tools/llvm-dwarfdump/X86/verify_strings.s

@@ -22,7 +22,7 @@ str_producer:
         .section .debug_abbrev,"",@progbits
         .byte 0x01  # Abbrev code
         .byte 0x11  # DW_TAG_compile_unit
-        .byte 0x01  # DW_CHILDREN_no
+        .byte 0x00  # DW_CHILDREN_no
         .byte 0x25  # DW_AT_producer
         .byte 0x1a  # DW_FORM_strx
         .byte 0x72  # DW_AT_str_offsets_base