commit-graph: remove unnecessary UNLEAK

When f4dbdfc (commit-graph: clean up leaked memory during write,
2018-10-03) added the UNLEAK, it was right before a call to die_errno().
e103f72 (commit-graph: return with errors during write, 2019-06-12)
made it unnecessary, as it was then followed by a free() call for the
allocated string.

The code moved to write_commit_graph_file() in the meantime and the
string pointer is now part of a struct, but the function's only caller
still cleans up the allocation.  Drop the superfluous UNLEAK.

Signed-off-by: René Scharfe <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

commit-graph.c

@@ -2055,7 +2055,6 @@ static int write_commit_graph_file(struct write_commit_graph_context *ctx)
 	}
 
 	if (safe_create_leading_directories(ctx->graph_name)) {
-		UNLEAK(ctx->graph_name);
 		error(_("unable to create leading directories of %s"),
 			ctx->graph_name);
 		return -1;