Foam: Fix the header pattern and remove unused bundled image

[iamtakashi]

Fix the header pattern and remove the unused bundled image.

[github-actions]

Preview changes

I've detected changes to the following themes in this PR: Foam.

You can preview these changes by following the links below:

• Preview changes for Foam

I will update this comment with the latest preview links as you push more changes to this PR.
⚠️ Note: The preview sites are created using WordPress Playground. You can add content, edit settings, and test the themes as you would on a real site, but please note that changes are not saved between sessions.

[github-actions]

Theme-Check results

foam: No changes required ✅.

💡 RECOMMENDED (2)

• No reference to register_block_pattern was found in the theme. Theme authors are encouraged to implement custom block patterns as a transition to block themes.
• No reference to register_block_style was found in the theme. Theme authors are encouraged to implement new block styles as a transition to block themes.

ℹ️ INFO (1)

• Only one text-domain is being used in this theme. Make sure it matches the theme's slug correctly so that the theme will be compatible with WordPress.org language packs. The domain found is foam.

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