Remove third-party block suggestions from the block inserter

[claytoncollie]

Description of the Change

Closes #267 by removing the third-party block suggestions from the block inserter. Also fixes the issue by removing the loading indicator when no blocks are found.

Closes #267

How to test the Change

1. clone repo
2. composer install in all themes and plugins
3. npm install and npm run build
4. activate theme
5. create new page
6. open block inserter
7. type none
8. verify third-party blocks are not in the inserter panel
9. repeat for the block theme.

Changelog Entry

Added - removed third-party block suggestions from block inserter

Credits

Props @claytoncollie @michael-sumner @fabiankaegy

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added Critical Flows, Test Cases, and/or End-to-End Tests to cover my change.
• All new and existing tests pass.

[fabiankaegy]

Love this! :)