Remove the unneeded @babel/no-invalid-this eslint disable rule

It looks like this line was a false positive for @babel/no-invalid-this
initially because here `this` comes from a parameter and it's not a
global `this`. After we upgraded the eslint version, this is correctly
caught and not reported as error.

I double checked this rule, by specifically making this mistake in the
codebase, and it looks like we catch it properly elsewhere, so it's not
a case where we fail to detect this rule.

This is the explanation of that rule:
https://eslint.org/docs/latest/rules/no-invalid-this

I explicitly tried the first incorrect example here and `yarn lint-js`
catches it properly.

Author: canova

src/test/components/MenuButtons.test.tsx

@@ -437,7 +437,6 @@ describe('app/MenuButtons', function () {
       jest.spyOn(Date.prototype, 'toLocaleString').mockImplementation(function (
         this: Date
       ) {
-        // eslint-disable-next-line @babel/no-invalid-this
         return 'toLocaleString ' + this.toUTCString();
       });