BUG/MINOR: stick-table: report the correct action name in error message

sc-inc-gpc() learned to use arrays in 2.5 with commit 4d7ada8f9 ("MEDIUM:
stick-table: add the new arrays of gpc and gpc_rate"), but the error
message says "sc-set-gpc" instead of "sc-inc-gpc". Let's fix this to
avoid confusion.

This can be backported to 2.5.
diff --git a/src/stick_table.c b/src/stick_table.c
index 99b1d33..507bd09 100644
--- a/src/stick_table.c
+++ b/src/stick_table.c
@@ -2579,7 +2579,7 @@
 	}
 	else {
 		/* default stick table id. */
-		memprintf(err, "invalid gpc ID '%s'. Expects sc-set-gpc(<GPC ID>,<Track ID>)", args[*arg-1]);
+		memprintf(err, "invalid gpc ID '%s'. Expects sc-inc-gpc(<GPC ID>,<Track ID>)", args[*arg-1]);
 		return ACT_RET_PRS_ERR;
 	}
 	rule->action = ACT_CUSTOM;