Changed Regex Validator for Phone Number Field for Patient Registration Form

[siddnikh]

Solves #1405
The landline numbers weren't getting accepted because the regex expected one of 4,5,6,7,8 or 9 after 0 in the starting of the phone number.
This won't work because most of the std codes start with 1 or 2 or 3.

[vigneshhari]

@sainak I am merging this MR, could you create an issue to add some tests for this change? ( or you can do it yourself! )