Update title, subtitle and plab CTA copy

[claudiucelfilip]

Changes proposed in this Pull Request

This makes the following copy changes:

Title: Choose your hosting plan.

Subtitle: The WordPress Pro plan comes with a 14-day money back guarantee

CTA for Pro plan: Start with Pro

Testing instructions

• Go to /start/plans?flags=plans/pro-plan and to plans/my-plan/[free_site]?flags=plans/pro-plan
• The title, subtitle and Pro plan CTA copy should match the summary:

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:commit-30da2f8147be75cee04e3a76837ce500b8e305c5

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:commit-30da2f8147be75cee04e3a76837ce500b8e305c5&env=jetpack

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Async-loaded Components (~15 bytes removed 📉 [gzipped])

name                           parsed_size           gzip_size
async-load-signup-steps-plans        -22 B  (-0.0%)      -15 B  (-0.0%)

React components that are loaded lazily, when a certain part of UI is displayed for the first time.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[southp]

Read much better :) Lets 🚢 this.

[a8ci18n]

This Pull Request is now available for translation here: https://translate.wordpress.com/deliverables/7211950

Thank you @claudiucelfilip for including a screenshot in the description! This is really helpful for our translators.

[a8ci18n]

Translation for this Pull Request has now been finished.