Map fixes for Britannia and Pangaea (#2641)

## Description:
This PR fixes some small pixel errors on Pangaea and Britannia

## 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

resources/maps/britannia/manifest.json

@@ -1,17 +1,17 @@
 {
   "map": {
     "height": 1396,
-    "num_land_tiles": 933706,
+    "num_land_tiles": 933571,
     "width": 2000
   },
   "map16x": {
     "height": 349,
-    "num_land_tiles": 55009,
+    "num_land_tiles": 54975,
     "width": 500
   },
   "map4x": {
     "height": 698,
-    "num_land_tiles": 228914,
+    "num_land_tiles": 228849,
     "width": 1000
   },
   "name": "Britannia",

resources/maps/pangaea/manifest.json

@@ -1,7 +1,7 @@
 {
   "map": {
     "height": 1000,
-    "num_land_tiles": 420336,
+    "num_land_tiles": 420335,
     "width": 1000
   },
   "map16x": {