increase nuke speed from 4 to 6 (#1125)

## Description:
Since nukes take a curved/longer paths nukes take too long to reach
their target. This PR increases their speed by 50%.

## 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:

evan

src/core/configuration/DefaultConfig.ts

@@ -752,7 +752,7 @@ export class DefaultConfig implements Config {
   }
 
   defaultNukeSpeed(): number {
-    return 4;
+    return 6;
   }
 
   // Humans can be population, soldiers attacking, soldiers in boat etc.