Fix disconnected Yalu River, KP/CN border (#4056)

## Description:

Fixes a portion of the river on the Nk/cn border of the korea map that
was disconnected from the ocean. Very minor fix

## 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 crunchybbbbb
<img width="1092" height="2149" alt="image6767"
src="https://github.com/user-attachments/assets/d53dfc55-cc7c-4fb6-8a12-cdf64bb1af87"
/>

---------

Co-authored-by: RickD004 <realtacoco@gmail.com>

resources/maps/korea/manifest.json

@@ -1,17 +1,17 @@
 {
   "map": {
     "height": 2148,
-    "num_land_tiles": 1194108,
+    "num_land_tiles": 1193914,
     "width": 1092
   },
   "map16x": {
     "height": 537,
-    "num_land_tiles": 71937,
+    "num_land_tiles": 71922,
     "width": 273
   },
   "map4x": {
     "height": 1074,
-    "num_land_tiles": 294112,
+    "num_land_tiles": 294064,
     "width": 546
   },
   "name": "Korea",