Improve Spain postcode regex

The two leftmost digits of a Spanish postal code correspond to the province codes. There are only 52 provinces, whose numbers range from 1 to 52.

Therefore, the regular expression could be a bit more precise, by allowing only valid province codes:
`^(?:0[1-9]|[1-4]\d|5[0-2])\d{3}$`

Source: https://en.wikipedia.org/wiki/Postal_codes_in_Spain

This is also done in Andorra "AD", where the third digit is one of the seven parishes, which is correctly limited by `[1-7]` in the regex.