Revert "[llvm][DebugInfo] DWARFv5: static data members declarations are DW_TAG_variable (#72234)"

This reverts commit 9a9933fa.

The OCaml bindings were using `LLVMDIBuilderCreateStaticMemberType`,
causing the API change in `9a9933fa`
to break buildbots that built the bindings. Revert until we figure out
whether to fixup the bindings or just not change the C-API