Rework / remove method reload_page

[JorjMcKie]

We previously refreshed a Page in memory by simulating navigating away to another page and returning. This has been necessary after certain updates or inserts of annotations and links. This fix basically replaces it with the feature provided by mupdf function pdf_sync_page(), which is now what Page method refresh() does.

This is a tentative update yet: As MuPDF propagates calling pdf_sync_page() over time, we should reduce and eventually retire Page.refresh() and Document.reload_page().