Revert default zoom type to “100%”

Issue #68431: Save zoom level with scores, keyboard shortcut for "Zoom to Page Width", ability to set default zoom to "Page Width" (and the corresponding PR #5623) added the ability to customize the default zoom type and also changed the default zoom type from “100%” to “Page Width”.

The latter change was welcomed by some but disliked by others. There was no consensus and there were some strong opinions on both sides, so I took a survey to try to get a better sense of what the user base as a whole would prefer.

There weren't a large number of responses to the survey (23), but the result was that there seemed to be a majority opinion that it would be better to go back to “100%” as the default zoom type.

Fortunately, it is very simple to change back. PR to follow.