Twenty Twenty-Five: Update patterns to fix accessibility issues

[joedolson]

There are four patterns in Twenty Twenty Five that raise flags:

• three patterns with full cover background images and no fallback colors. These raise contrast errors, and would cause problems if images were not available. Minor issues, but easily addressed.

• The event 3 col pattern uses repeating link text which matches a pattern that a user might actually use, leading to redundant link text. Updates the text to have variation, and to encourage users to change it.

Trac ticket: https://core.trac.wordpress.org/ticket/66181

Use of AI Tools

None.

Poster-like section

Before	After

Events, 3 columns with event images and titles

Hero, full width image

Coming soon

[mukesh27]

Mark ready for commit