Fix typo for %I delimiter check

[Earlopain]

Also add tests for the other types which currently don't have one

[schneems]

Thanks. To clarify for others, without this fix it will incorrectly report this code

          node.is_a?(Op) && %I[| ||].include?(node.value) &&

As missing a [

Failures:

  1) ExplainSyntax handles %I-style array
     Failure/Error: expect(explain.missing).to eq([])
     
       expected: []
            got: ["["]
     
       (compared using ==)