Fix non valid SafeString flag codes (#1135)

## Description:
Removed unicode in the following flag file names to prevent error, which
lead to not be able to start a game with it.

- Ceará
- 1_Northern Uí Néill
- Pará
- São Paulo
- 1_Southern Uí Néill

related to https://github.com/openfrontio/OpenFrontIO/pull/1133

## 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:

ghisloufou

resources/maps/Britannia.json

@@ -115,7 +115,7 @@
       "coordinates": [564, 845],
       "name": "Southern Uí Néill",
       "strength": 3,
-      "flag": "1_Southern Uí Néill"
+      "flag": "1_Southern Ui Neill"
     },
     {
       "coordinates": [639, 680],
@@ -133,7 +133,7 @@
       "coordinates": [416, 678],
       "name": "Northern Uí Néill",
       "strength": 3,
-      "flag": "1_Northern Uí Néill"
+      "flag": "1_Northern Ui Neill"
     },
     {
       "coordinates": [1869, 1308],