Do not apply hovercards on tickets within link tags

[swissspidy]

As can be seen on ​https://make.wordpress.org/cli/handbook/wish-list/, the ticket preview script fails when trying to load information for a ticket. The tickets exist, but of course reference GitHub issues, not Trac tickets.

Given that these ticket numbers are within existing <a> tags, I think the hovercard script should skip any already linked tickets.

[ocean90]

Well, the script only works if tickets/changesets are inside of link tags so we can't skip them. Maybe we should just make them work with GitHub links.

[SergeyBiryukov]

Related: #2440

[SergeyBiryukov]

Is ​https://github.com/Automattic/p2-hovercards the relevant code, or is it a custom dotorg script? Looking at #1167, seems like the latter.

[obenland]

Duplicate of #2440.