Disable Appstream runner by default
There have been repeated complaints about this runner, for instance that takes a lot of CPU, the results are ordered to high and the results are straight-up not relevant.
A little rant can be found here: https://www.reddit.com/r/kde/comments/hp9a6c/why_does_krunner_prefer_the_software_center_over/ The image also shows that the logic if an app is already installed does not work that well.
And IMHO this runner is not that useful to most people. If someone want to search for software they will most likely use discover where they have preview images, descriptions and rating.
And since the very useful spellchecker runner is now enabled by default it seems fair to me that we can disable one of the not so useful runners ;)