xfs: remove unused trace event xfs_reflink_cow_enospc

xfs: remove unused trace event xfs_reflink_cow_enospc

The call to the event xfs_reflink_cow_enospc was removed when the COW
handling was merged into xfs_file_iomap_begin_delay, but the trace event
itself was not. Remove it.

Fixes: db46e604adf8 ("xfs: merge COW handling into xfs_file_iomap_begin_delay")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>