This commit fixes 2 issues:
- a UX issue described by tdf#124544 (slideshow spinner is not
displayed for the correct duration - user shown a blank screen while the
browser downloads slideshow.svg)
- an additional HTTP request is being made to loading.html just to
display an ordinary spinner (that can be otherwise loaded via css for
example)
tdf#124544
Change-Id: I90d1e73d1514d736dd58a53caa5921b42bc1bd75
Reviewed-on: https://gerrit.libreoffice.org/70250
Reviewed-by: Szymon Kłos <szymon.klos@collabora.com>
Tested-by: Szymon Kłos <szymon.klos@collabora.com>
