Minor fixes to plagiarize script commands (#7394)

* Fix plagiarizeskillreset unable to reset.
* Update plagiarizeskill documentation.

doc/script_commands.txt

@@ -6309,6 +6309,10 @@ it just removes non-permanent script.
 Enable the player to plagiarize specific skills that are copyable.
 Return 1 on success, 0 otherwise.
 
+Note:
+ - Plagiarism only able to copy skill while SC_PRESERVE is not active and skill is copyable by Plagiarism.
+ - Reproduce can copy skill if SC__REPRODUCE is active and the skill is copyable by Reproduce.
+
 ---------------------------------------
 
 *plagiarizeskillreset <flag>;

src/map/script.cpp

@@ -10191,7 +10191,7 @@ BUILDIN_FUNC(plagiarizeskillreset)
 {
 	TBL_PC *sd;
 
-	if (!script_rid2sd(sd))
+	if (script_rid2sd(sd))
 		script_pushint(st, pc_skill_plagiarism_reset(*sd, script_getnum(st, 2)));
 
 	return SCRIPT_CMD_SUCCESS;