Update newspack blocks to v1.20

[noahtallen]

• bump newspack blocks to v1.20
• includes fix for specific posts selection
• includes fixes for all phpcs issues

Test plan:

1. load these changes on a sandbox and verify that newspack blocks works, and that the issues mentioned in this PR (refactor: get specific posts REST endpoint from localized value newspack-blocks#689) are fixed.

[matticbot]

Test live: https://calypso.live/?branch=update/newspack-blocks

[matticbot]

Caution: This PR affects files in the Editing Toolkit Plugin on WordPress.com
Please ensure your changes work on WordPress.com before merging.

D56595-code has been created so you can easily test it on your sandbox. See this FieldGuide page about developing the Editing Toolkit Plugin for more info: PCYsg-ly5-p2

[matticbot]

This PR does not affect the size of JS and CSS bundles shipped to the user's browser.

Generated by performance advisor bot at iscalypsofastyet.com.

[dkoo]

@noahtallen The updated package looks good on my sandbox. I also pushed a fix in 798f7c4 which will close Automattic/newspack-blocks#687 for Atomic sites. To test, run yarn run build first and make sure it pulls down the new amp/homepage-posts/view.js file into the synced-newspack-blocks folder. Then:

1. On a test or ephemeral Atomic site, rsync or manually zip the contents of /apps/editing-toolkit/editing-toolkit-plugin and install/activate as a plugin.
2. Activate the AMP plugin (should be installed on Atomic sites by default) and turn on Standard or Transitional mode.
3. Create a post and add a Blog Posts block in query mode. Turn on the "load more" option and make sure there are enough posts loading to show the load more functionality.
4. View the post's front-end with AMP on and confirm that the "load more" button works as expected.

[noahtallen]

Cool, I'll also give that a test!

[dkoo]

Adding to note that this will address #49707 (but will not close it until ETK is fully redeployed).

[dkoo]

Approving for 84f1d2d—if the Atomic fix looks good to you, feel free to merge, or @jeffersonrabb can also review if we need a third set of eyes.