Update Halkidiki.json (#809)

## Description:
Fixed wording in Halkidiki.json

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [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:

<DISCORD USERNAME>
Nikola123

resources/maps/Halkidiki.json

@@ -1,5 +1,5 @@
 {
-  "name": "Chalkidiki",
+  "name": "Halkidiki",
   "width": 2200,
   "height": 1760,
   "nations": [