Stop using SearchUpdate::updateText()

- It's only really useful on wikitext, which we explicitly aren't
- Only useful thing it does is strip html, so we'll just move that
  bit to buildTextToIndex() since we already do it on wikitext

Change-Id: I97adbc9fa9b06bd353ffc54d29790fcb021a66c3
Merge "Stop using SearchUpdate::updateText()"