changed regex to accept Top-level domain with length 63

[bluedskim]

Hi,

According to IETF, A TLD label MUST be at least two characters long and MAY be as long as 63 characters. https://tools.ietf.org/id/draft-liman-tld-names-00.html#:~:text=A%20TLD%20label%20MUST%20be,or%20trailing%20periods%20(.).

changed max length value of the regular expression.