Remove id searchbox on mobile to fix a layout bug

[obulat]

Sphinx in doctools.js uses an element with id searchbox to append a paragraph saying "Hide search matches". It is currently not used in the Python docs, but with the responsive theme, it breaks the layout. The search box at the top has a "Hide search matches" link to the right of it:

To reproduce:

1. Go to the 3.11 version of the docs
2. Narrow your screen to mobile width
3. Search for something (eg. "xml rpc")
4. Click on one of the search results (eg. "xmlrpc.client — XML-RPC client access")

I removed the id from the search form in the top menu bar so that this link is not added.

[JulienPalard]

Thanks!