phone-number: Updated the exercise to the 1.6.1 version

[ZapAnton]

Relevant PRs:

• phone-number: Remove test using malformed input. problem-specifications#772
• phone-number: add missing edge cases problem-specifications#1090
• phone-number: Apply new "input" policy problem-specifications#1120
• phone-number: add cases to test data that cover invalid use of "1" or "0" problem-specifications#1327
• implement error object on multiple exercises problem-specifications#1337
• Phone-Number: Resolved some inconsistencies in error messages. problem-specifications#1361

The old example solution did not pass some new tests, so I replaced it with my own old solution, which may be not too optimal, but it passes all the tests

[coriolinus]

Looks good! I'll plan to merge this on Friday unless there are objections.

[petertseng]

I identified two duplicates that you could consider deleting. In fact I even recommend it since some of them have slightly confusing names.