Synchronized tests for phone-number exercise

[dr-impossible]

This PR is to update the tests for the phone-numbers exercise. The tests which check for symbols or letters would result in false positives if the code ensures that the area code or exchange code begin with a digit in range 2-9.

This also updates the exercise description to match the problem-specification.

The example solution passes the updated tests, so no change was needed there.

The updated specs for "invalid when more than 11 digits" and "invalid when 9 digits" have no change since the Haskell tests don't check for an error message

[github-actions]

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[github-actions]

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[no important files changed]

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