Fix: invalid token checking in computed-property-spacing (fixes #12198)

[yeonjuan]

What is the purpose of this pull request? (put an "X" next to item)

[ ] Documentation update
[x] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[ ] Add autofixing to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

What changes did you make? (Give an overview)

Fix it #12198

Is there anything you'd like reviewers to focus on?

[kaicataldo]

Thanks for working on this! Can we include some more complex regression tests like the following?

const foo = {
  [ a[b] ]: 1
}

const bar = {
  [ a/**/ [b /**/ ] ]: 1
}

[yeonjuan]

@kaicataldo
I added more complex test cases.:)

[kaicataldo]

Thank you for contributing! This LGTM.

[btmills]

Thanks for this @yeonjuan! This is much more robust.