Buttons block: Use default background color based on the current theme

[fluiddot]

Description

When adding a Buttons block, the background color of buttons is always set to grey by default. This diverges from the web version, which uses the default color based on the theme.

Step-by-step reproduction instructions

1. Add a Buttons block in the web version.
2. Check the background color applied to the button.
3. Add a Button block in the native version.
4. Observe that the background color is grey and doesn't match the one observed in the web version.

Expected behaviour

By default, buttons of the Buttons block should have their background color based on the current theme.

Actual behaviour

By default, buttons of the Buttons block always have their background set to grey.

Screenshots or screen recording (optional)

Web	App

WordPress information

• WordPress version: N/A
• Gutenberg version: N/A
• Are all plugins except Gutenberg deactivated? N/A
• Are you using a default theme (e.g. Twenty Twenty-One)? No

Device information

• Device: iPhone 11
• Operating system: iOS 15.4.1
• WordPress app version: WP-iOS 23.2.0.0