Update libphonenumber dependency to 7.2.3 or later

[msymons]

Update com.googlecode.libphonenumber:libphonenumber from 6.2 to 7.2.3 or later. Current version is 8.3.3.

This addresses an XSS vulnerability

The vulnerability is identified in Sonatype Nexus IQ analysis with reference SONATYPE-2015-0090.

Would you like me to do a PR?

[Capstan]

Fixed in commit c2379dc