Bump the propresenter parser to dev-master (20fe32a), which brings the
background-layer and nametag-subtitle features onto the consumed
bussnet/propresenter7-php-api branch and resolves the
Slide::hasBackgroundMedia() regression. Strengthen AbspannExportTest to
assert the now-live 10s auto-advance loop (completion AFTER_TIME == 10,
target FIRST) and the Dissolve transition (renderId EC52A828-...).
