Create_member no longer gets called twice (#7057)

# About the pull request

mob_max is inclusive, and we start at zero.
# Explain why it's good for the game
 resolves #7053 

![image](https://github.com/user-attachments/assets/1d732615-e305-4b74-8d9f-68232abaead0)

It was kinda sad....
# Testing Photographs and Procedure
<details>
<summary>Screenshots & Videos</summary>

Put screenshots and videos here with an empty line between the
screenshots and the `<details>` tags.

</details>


# Changelog
:cl:
fix: ERT no longer gets one extra free member in freed mobs if the
beacon wasnt completely taken
/:cl:

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Co-authored-by: harryob <[email protected]>

code/datums/emergency_calls/emergency_call.dm

@@ -324,7 +324,7 @@
 
 
 	if(spawn_max_amount && i < mob_max)
-		for(var/c in i to mob_max)
+		for(var/c in i to mob_max - 1)
 			create_member(null, override_spawn_loc)
 
 	candidates = list()