Reduces ship spawn limit for everything to 1 (#3166)

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## About The Pull Request

Reduces the spawn limit for every ship to 1, and makes the default limit
for new ships 1.

## Why It's Good For The Game

Nearly every ship was already set to a limit of 1. Making it the default
just saves time. Most of the handful of ships that still had a cap of 2-
mudskipper, li tieguai, and delta, for instance - were ships that would
just compete for pop or nudge each other out of their niche if
double-spawned, and a greater variety of ships are available to accept
players after existing ones fill up than there previously were.

## Changelog

:cl:
balance: reduced default ship spawn limit to 1.
/:cl:

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_maps/configs/independent_beluga.json

@@ -12,7 +12,7 @@
 		"Service"
 	],
 	"starting_funds": 4000,
-	"limit": 2,
+	"limit": 1,
 	"job_slots": {
 		"Captain": {
 			"outfit": "/datum/outfit/job/independent/captain",

_maps/configs/independent_mudskipper.json

@@ -14,7 +14,7 @@
 		"SPACE"
 	],
 	"map_path": "_maps/shuttles/independent/independent_mudskipper.dmm",
-	"limit": 2,
+	"limit": 1,
 	"starting_funds": 1500,
 	"job_slots": {
 		"Salvage Leader": {

_maps/configs/independent_schmiedeberg.json

@@ -14,7 +14,7 @@
 		"SUNS",
 		"GENERAL"
 	],
-	"limit": 2,
+	"limit": 1,
 	"job_slots": {
 		"Chief Pharmacist": {
 			"outfit": "/datum/outfit/job/independent/cmo/pharma",

_maps/configs/nanotrasen_gecko.json

@@ -14,7 +14,7 @@
 		"Mining",
 		"Engineering"
 	],
-	"limit": 2,
+	"limit": 1,
 	"starting_funds": 5000,
 	"job_slots": {
 		"Captain": {

_maps/example_ship_config.json

@@ -5,7 +5,7 @@
 	"prefix": "STSV",
 	"namelists": ["GENERAL", "SPACE", "MYTHOLOGICAL", "WEAPONS"],
 	"map_path": "_maps/shuttles/shiptest/null.dmm",
-	"limit": 2,
+	"limit": 1,
 	"spawn_time_coeff": 1.5,
 	"officer_time_coeff": 0.5,
 	"job_slots": {

_maps/ship_config_schema.json

@@ -134,7 +134,7 @@
 			"description": "The amount of ships that can be spawned in by players in a round at once.",
 			"minimum": 0,
 			"maximum": 100,
-			"default": 2
+			"default": 1
 		},
 		"starting_funds":{
 			"title": "Ship Starting Funds",