Optimize the speed of the gettext command

What does this MR do and why?

Related issue: #2789 (closed)

1. Follow Upstream's practice, use GettextExtractor instead of gettext:pot:create (Saved 2s)
2. No longer load meaningless dependency (Saved 7s !)

	Average time spent on "bin/rake jh:gettext:regenerate"
Before	🕙 🕙 🕙 🕙 🕙 🕙 🕙 🕙 🕙 🕙 🕙 🕙 🕙 🕙 🕙 15s
After	🕙 🕙 🕙 🕙 🕙 🕙 6s

Screenshots or screen recordings

No UI changes.

How to set up and validate locally

Randomly modify a JH i18n text, execute bin/rake jh:gettext:regenerate.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.