Remove require of search-with-autocomplete JS

This javascript is now provided by static [1] and is thus removed from
this repo to ensure that we don't send the same asset to users
multiple times unnecessarily.

It continues the convention of applications only adding the JS of
components which are not provided by static [2].

[1]: alphagov/static#3532
[2]: #2819

app/assets/javascripts/application.js

@@ -17,7 +17,6 @@
 //= require govuk_publishing_components/components/metadata
 //= require govuk_publishing_components/components/option-select
 //= require govuk_publishing_components/components/radio
-//= require govuk_publishing_components/components/search-with-autocomplete
 //
 //= require govuk_web_banners/dependencies
 //