Upgrade to suport recent version of click.

[majkrzak]

Installing mbed-tools is locket on systems where recent Click is installed, for example where black formatting tools is used. Please upgrade Click requirement to the latest version.

[Apteryks]

I've tested relaxing the version of Click to accept 8, and the test suite passed:

======================= 631 passed, 27 skipped in 6.39s ========================

[0xc0170]

Can you send the PR updating the version?

[BioBox]

Yeah, can you do that please?