Adapt kfilemetadata to "audio/x-speex+ogg" as recently changed in shared-mime-info
commit 479b17f6639844acdc061fa6 in shared-mime-info has changed the mimetype for our test.spx file, adapt so that EmbeddedImageDataTest still passes
Noticed the failure on CI
Reproduced locally by installing shared-mime-info from git into /usr/local, running update-mime-database there, and then
XDG_DATA_DIRS=/usr/local/share bin/embeddedimagedatatest