Rev: Update "Japan and Neighbors" map to "East Asia" (#1007)

**Closes Issue #1001.**

_Will require updates to translations for each language but English is
in place as are pointers to relevant map files and thumbnails._

## Description:
All assets and references to the Japan and Neighbors map have been
updated to reflect East Asia.

**New Behavior**
![East Asia
Map](https://github.com/user-attachments/assets/64192590-bbb7-4408-a99b-7455de295d2b)

**Old Behavior**
![Japan and Neighbors named
map](https://github.com/user-attachments/assets/ba44dd56-1470-4c74-a70d-bd7fd8f3c795)

Game test is functioning. Other languages will need to be updated for
their displayed text to align.

## 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
- [x] I understand that submitting code with bugs that could have been
caught through manual testing blocks releases and new features for all
contributors

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

ajaxburger
_My git name is included in my nickname on the server._

---------

Co-authored-by: evanpelle <evanpelle@gmail.com>

resources/lang/cs.json

@@ -135,7 +135,6 @@
     "random": "Náhodná",
     "iceland": "Island",
     "pangaea": "Pangea",
-    "japan": "Japonsko a okolí",
     "betweentwoseas": "Mezi dvěma moři",
     "knownworld": "Známý svět",
     "faroeislands": "Faerské ostrovy",