Cleanup: ctf-writer: field-wrapper.c: logically dead code

Cleanup: ctf-writer: field-wrapper.c: logically dead code

Coverity reported the following:
  CID 1401191 (#1 of 1): Logically dead code (DEADCODE)dead_error_begin:
  Execution cannot reach this statement: bt_ctf_field_wrapper_destroy.

Reported-by: Coverity - 1401191 Logically dead code (DEADCODE)
Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: Ib468f8df4a11491b185ffa45c2db3bc4fc8fb045
Reviewed-on: https://review.lttng.org/c/babeltrace/+/2051
Tested-by: jenkins <jenkins@lttng.org>
Reviewed-by: Simon Marchi <simon.marchi@efficios.com>