remove display of content mimetype

serv_got_im is triggering an access violation on mimetype with some
systems. This metadata is not necessary and purely informational.
3 jobs for mmsd in 4 minutes and 14 seconds (queued for 3 seconds)
latest
Status Name Job ID Coverage
  Build
passed build-debian-gcc-buster #313262
librem5

00:00:45

 
  Package
passed package:deb-debian-buster #313263
librem5

00:00:58

passed package:deb-debian-buster:arm64 #313264
librem5:arm64

00:03:29