This redirect was supervened for {{search link}} → {{sl}}, and family ({{slre}}, and {{slte}}).
These arose in response to the needs of Wikipedia:Searching. The new CirrusSearch engine offers regular expressions, but these need special templates in order for users to develop and provide proven regular expression searches that can safely run on the Wikipedia search engine.
Without an easy way to develop regex searches, such as
- easy template names, like sl, slre, and slte
- easy parameter usage, like using a named parameter or not, and having productive default parameters
- use on any preview page to test any regexp
then two bad things might happen. The fun and allure of a shortcut is lost (necessitating the longer name s e a r c h l i n k every time. 1) Untested, useless, buggy regex might crowd the search engine out of useful regex more often. (The number of regexp searches are technically restricted for performance reasons.) and 2) More and more people might not begin to learn and practice-via-{{sl}} the new Cirrus Search Search engine's regex aspects, and so less people might be inclined to improve Wikipedia by bringing nuanced, detailed searches offered by exactitude of regex searches, in order to bring to light things otherwise impossible to enumerate, and so decision making would have to remain tilted toward blind bias.
See also this related information:
That last bot changes wikitext {{sl}} → {{sl icon}}. It hasn't run in a while, and I only had to change a few wikitext instances so that "what links here" (on the template page), is now only from user space, Templates for discussion logs, or template documentation, i.e. nothing as important as helping Wikipedia Search.