Fix the Strait Of Gibraltar map (#2080)

## Description:
This PR fixes the rivers not showing up on the map in-game.

Describe the PR.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

DISCORD_USERNAME
Nikola123

map-generator/generated/maps/straitofgibraltar/manifest.json

@@ -1,12 +1,12 @@
 {
   "map": {
     "height": 1476,
-    "num_land_tiles": 1998085,
+    "num_land_tiles": 1942981,
     "width": 2902
   },
   "mini_map": {
     "height": 738,
-    "num_land_tiles": 498123,
+    "num_land_tiles": 483724,
     "width": 1451
   },
   "name": "Strait of Gibraltar",

resources/maps/straitofgibraltar/manifest.json

@@ -1,12 +1,12 @@
 {
   "map": {
     "height": 1476,
-    "num_land_tiles": 1998085,
+    "num_land_tiles": 1942981,
     "width": 2902
   },
   "mini_map": {
     "height": 738,
-    "num_land_tiles": 498123,
+    "num_land_tiles": 483724,
     "width": 1451
   },
   "name": "Strait of Gibraltar",