Remove and replace title attributes from theme list tables

[sabernhardt]

• Removes title attributes from span elements.
• Replaces title with aria-label for links whose visible text starts with the same word (in English). This is similar to links on the Add Plugins screen.
• Reuses the $preview_title variable to keep ARIA labels consistent for both Preview links.

Trac 62834

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Props sabernhardt.

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[github-actions]

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[audrasjb]

Good to go!

[audrasjb]

committed in https://core.trac.wordpress.org/changeset/59675