chore(android): remove `other-polyfills.js` from `keyboard.html`

`other-polyfills.js` defines `DOMRect` which wasn't available until Chrome 61. However, our minimum Chrome version is now 95, so we can safely delete this file, and the reference in `keyboard.html`.

Start by opening keyboard.html and locating its reference to other-polyfills.js, then inspect the polyfill file and the surrounding keyboard page setup. Remove the obsolete file and its reference; the work is done when the page no longer loads it and the keyboard page still builds or runs as expected.

Written by the indexing model from the issue text.