Update the Iris color picker to version 1.0.6.

Changes: https://github.com/Automattic/Iris/compare/1.0.4...1.0.6

props mattwiebe.
fixes #30365.
Built from https://develop.svn.wordpress.org/trunk@30551


git-svn-id: http://core.svn.wordpress.org/trunk@30540 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Customizer: Don't override `Section.isContextuallyActive()` in `SidebarSection`.

This fixes a bug where empty widget areas get deactivated in the Customizer.

fixes #30378.
see #30235.
props westonruter.
Built from https://develop.svn.wordpress.org/trunk@30552


git-svn-id: http://core.svn.wordpress.org/trunk@30541 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Customizer: Only show the default button in the upload control if there is a default attachment.

props celloexpressions.
see #21483.
Built from https://develop.svn.wordpress.org/trunk@30553


git-svn-id: http://core.svn.wordpress.org/trunk@30542 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Clear update caches when site language is changed.

The update screen has a re-install button which could show the wrong language locale after the site language was changed. That's because the update data is cached. 
Introduce `_wp_clear_update_cache()` as a helper function to clean up the update cache.

props SergeyBiryukov, ocean90.
fixes #30369.
Built from https://develop.svn.wordpress.org/trunk@30554


git-svn-id: http://core.svn.wordpress.org/trunk@30543 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Improve the focus style for review links in the plugin info modal.

props johnbillion.
fixes #30375.
Built from https://develop.svn.wordpress.org/trunk@30555


git-svn-id: http://core.svn.wordpress.org/trunk@30544 1a063a9b-81f0-0310-95a4-ce76da25c4cd