The current 25k limit is preventing various normal editing activities, such as embedding navigation-templates (for discussion/illustration) or header-area templates. We should increase the limit.

Context: https://gerrit.wikimedia.org/r/#/c/159805/ ("Limit expanded content to 25kB per revision") was implemented in September, to prevent problems with people transcluding entire noticeboards/talkpages, causing mass pings (T52082). At the same time, we implemented https://gerrit.wikimedia.org/r/#/c/159804/ ("Limit notifications to 20 per post") for Flow, and then a month later the same for general Echo https://gerrit.wikimedia.org/r/#/c/159800/ ("Limit Echo mentions to 20 users").