API: Update error message of ns.singularity.joinFaction (#2700)

src/ScriptEditor/NetscriptDefinitions.d.ts

@@ -2362,8 +2362,10 @@ export interface Singularity {
    *
    * This function will automatically accept an invitation from a faction and join it.
    *
+   * Note that this function returns false if you are already a member of the specified faction.
+   *
    * @param faction - Name of faction to join.
-   * @returns True if player joined the faction, and false otherwise.
+   * @returns True if the player successfully accepts an invitation, and false otherwise.
    */
   joinFaction(faction: FactionName): boolean;