Get rid of isValidNumberPrecise

[jackocnr]

NOTE: if you vote no, please add a comment describing your use cases below.

Since v19.0.0, we changed our default validation method, isValidNumber, from using libphonenumber's precise validation method (checking specific digit ranges/area codes etc) to its practical validation method (just checking the number length), because it is much more stable and less likely to break as number systems around the world change all the time. We made the precise validation method available as isValidNumberPrecise, but since then I have increasingly thought that this is not really useful, for 2 reasons. Firstly, it is prone to breaking (rejecting valid numbers) unless it is constantly updated, and secondly, it just overcomplicates things e.g. devs having to read the docs to decide which kind of validation they want to use, and the demo site needing to have 2 menu options: "Validation (Practical)" and "Validation (Precise)" - I think this is confusing.

For these reasons, I propose we drop it. I think that for the purposes of this plugin, the practical validation method is much more reliable and should be more than enough for the average use case of taking someone's mobile number.

[jackocnr]

I decided to keep it, but mark it as DANGEROUS with the recommendation to only use it if you setup a script to automatically keep it up-to-date, so your site doesn't start rejecting valid numbers.