Rustdoc search is broken on mobile

[jyn514]

Steps to reproduce (@pickfire used firefox on mobile):

1. go to search page
2. type something to search
3. blue the search (keyboard lowers)
4. you cannot click on search bar anymore

Oh, I just found out that it works except the click position is way out, you need to touch the corner of the screen rather than the center of the box itself.

Originally posted by @pickfire in #77333 (comment)