Update mobile code for changes in color settings/attributes

[SergioEstevao]

Gutenberg PR: WordPress/gutenberg#21257

To test:

• Start the demo app
• Make sure post open
• Copy blocks from the web where custom colors are set
• For example paragraph blocks:

<!-- wp:paragraph {"style":{"color":{"text":"#9bc2d3"}}} -->
<p style="--wp--color--text:#9bc2d3" class="has-text-color">text</p>
<!-- /wp:paragraph -->

Check that after switching from HTML to visual the settings on the block are kept.

PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.