docs: bump install one-liner minimum to Node.js 25 (#402)

Etherpad is moving its supported runtime floor to Node.js >= 25.
Update the install hint on the homepage so the prerequisite line
matches the project's documented minimum.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: JohnMcLear

src/components/InstallOneLiner.tsx

@@ -70,7 +70,7 @@ export const InstallOneLiner = () => {
             </button>
         </div>
         <p className="text-xs text-gray-500 dark:text-gray-400 px-3 pb-3">
-            Needs <code>git</code> and Node.js &ge; 20. Then <code>cd etherpad && pnpm run prod</code> and open <code>http://localhost:9001</code>.{' '}
+            Needs <code>git</code> and Node.js &ge; 25. Then <code>cd etherpad && pnpm run prod</code> and open <code>http://localhost:9001</code>.{' '}
             <a
                 href="https://github.com/ether/etherpad#installation"
                 target="_blank"