Fix modifierkey setting for mac (#2327)

## Description:

Currently not an issue, but this is a code smell in case we ever decide
to have it editable, current implementation will make the default
overwrite the custom setting

Pointed out by  #1804


## 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

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

Mr. Box

src/client/InputHandler.ts

@@ -167,6 +167,9 @@ export class InputHandler {
       console.warn("Invalid keybinds JSON:", e);
     }
 
+    // Mac users might have different keybinds
+    const isMac = /Mac/.test(navigator.userAgent);
+
     this.keybinds = {
       toggleView: "Space",
       centerCamera: "KeyC",
@@ -180,7 +183,7 @@ export class InputHandler {
       attackRatioUp: "KeyY",
       boatAttack: "KeyB",
       groundAttack: "KeyG",
-      modifierKey: "ControlLeft",
+      modifierKey: isMac ? "MetaLeft" : "ControlLeft",
       altKey: "AltLeft",
       buildCity: "Digit1",
       buildFactory: "Digit2",
@@ -195,12 +198,6 @@ export class InputHandler {
       ...saved,
     };
 
-    // Mac users might have different keybinds
-    const isMac = /Mac/.test(navigator.userAgent);
-    if (isMac) {
-      this.keybinds.modifierKey = "MetaLeft"; // Use Command key on Mac
-    }
-
     this.canvas.addEventListener("pointerdown", (e) => this.onPointerDown(e));
     window.addEventListener("pointerup", (e) => this.onPointerUp(e));
     this.canvas.addEventListener(