==Remove instrumentation language switching
The language button instrumentation relies on a scroll event handler and on `mw.viewport.isElementInViewport()`, which [[ http://dcousineau.com/blog/2013/09/03/high-performance-js-tip/ | forces a style recalc ]]. The simplest way to fix this would be to remove the instrumentation, if we have accumulated enough data.
Furthermore, once we've collected sufficient data, we won't need the modal eventing anymore, either.
== [Done] Remove feature `MinervaUsePageActionBarV2`
This supports the old page actions bar which didn't have the language icon.
Supporting 2 modes of page actions is no longer necessary.
[x] Remove checks for MinervaUsePageActionBarV2 and need for variable
[x] Remove use of `feature-page-action-bar-v2` class
==Remove feature `MinervaBottomLanguageButton`
The bottom language button is feature flagged using that variable. Remove the HTML generation in SkinMinerva.php, the related CSS rules to `#page-secondary-actions .language-selector`, and related JS code that enables this button to work (is kind of shared with the page-actions one, so maybe there's not that much to remove).
[ ] Language button related event logging is disabled
[ ] [[ https://meta.wikimedia.org/wiki/Schema:MobileWebLanguageSwitcher | Language button related schemas ]] are marked as inactive
[x] Action bar styles and feature flags are unflagged and stabilized (grep for T130849 to find `FIXME`s)