Keyboard not working when showTimeSelectOnly is True

[feardarkness]

Describe the bug You can't pick a time with the keyboard when showTimeSelectOnly=true.

To Reproduce Steps to reproduce the behavior:

1. add showTimeSelectOnly=true to the component
2. Try to navigate with the keyboard arrows

Expected behavior We should be able to move/pick a time with the keyboard arrows

• Version: "react-datepicker": "^6.8.0"

Additional context You can test it in the official site: https://reactdatepicker.com/#example-select-time-only

[alvaromartinez986]

I can work on that