Prevent update selected styles when text changes on Gutenberg mode

[fluiddot]

Related to Gutenberg PR: WordPress/gutenberg#37676

Gutenberg already controls the selected styles, so we need to prevent Aztec from modifying them when the text changes.

Test

This change shouldn't affect the current behavior of the selected styles hence, we should just verify that Aztec works as expected regarding the selected styles when modifying text.

Review

@guarani
@antonis

Make sure strings will be translated:

• If there are new strings that have to be translated, I have added them to the client's strings.xml as a part of the integration PR.

[antonis]

Great work @fluiddot 👍
I tested the change with a local Android build and everything work as expected. The code change looks consistent to me 🎉

[guarani]

I see this is already approved but I gave it a quick test on Android and it works as expected 👍 Also the code changes on both platforms look very similar.
Thanks for fixing this issue, @fluiddot!