#7701: Update README.md

Update README.md typo fix <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR makes a one-word typo/spelling correction in `vendor/a2ui/README.md`, changing “updateable” to “updatable” in the A2UI description. No code or behavior changes are involved; it’s purely documentation text within the vendored A2UI README. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge; it’s a trivial documentation typo fix. - Only a single word is changed in a README under `vendor/`, with no effect on runtime behavior, build, or tests. The change improves wording and does not introduce links, formatting breakage, or other downstream impacts. - No files require special attention <!-- greptile_other_comments_section --> _{(3/5) Reply to the agent's comments like "Can you suggest a fix for this @greptileai?" or ask follow-up questions!} **Context used:** - Context from `dashboard` - CLAUDE.md ([source](https://app.greptile.com/review/custom-context?memory=fd949e91-5c3a-4ab5-90a1-cbe184fd6ce8)) - Context from `dashboard` - AGENTS.md ([source](https://app.greptile.com/review/custom-context?memory=0d0c8278-ef8e-4d6c-ab21-f5527e322f13)) <!-- /greptile_comment -->