Enable the prefer-destructuring eslint rule (#1858)

## Description:

Enable the `prefer-destructuring` eslint rule.

## 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

src/core/game/PlayerImpl.ts

@@ -846,7 +846,7 @@ export class PlayerImpl implements Player {
     if (existing.length === 0) {
       return false;
     }
-    const unit = existing[0].unit;
+    const { unit } = existing[0];
     if (!this.canUpgradeUnit(unit.type())) {
       return false;
     }