Block Editor: Bug fixes targeted for WordPress 5.3.1.

The list of included fixes:

- Edge scrolling issues https://github.com/WordPress/gutenberg/pull/17707
- Intermittent JavaScript issues https://github.com/WordPress/gutenberg/pull/18559
- Remove embed CollegeHumor https://github.com/WordPress/gutenberg/pull/18591 

Updated packages:

- @wordpress/block-directory@1.0.6
- @wordpress/block-editor@3.2.5
- @wordpress/block-library@2.9.6
- @wordpress/core-data@2.7.5
- @wordpress/edit-post@3.8.6
- @wordpress/editor@9.7.6
- @wordpress/format-library@1.9.5

Props youknowriad, ellatrix, epiqueras, audrasjb, gziolo, mcsf, kyliesabra.
Fixes #48884.
Built from https://develop.svn.wordpress.org/trunk@46860


git-svn-id: https://core.svn.wordpress.org/trunk@46660 1a063a9b-81f0-0310-95a4-ce76da25c4cd