fdo#81835 Don't prefer GDI Metafiles to RTF/HTML -- correctly.

Was first introduced by 538c13f3d1756f2d105115f64ab1bc0b7426eebc

We should process clipboard formats in order of descriptive-/
usefulness -- however png/bmp are special cases (as browsers
will add an html equivalent to their clipboard when copying raw
images, with the raw image being the preferred target format)
and were therefore moved up in the paste-preference list,
mistakenly it was assumed that GDI Metafiles should be subject
to the same treatment, but it appears that Word (and Wordpad?)
will provide both RTF (preferred) and GDI for formatted text.

Change-Id: I731986fc9d70e7aeb64e53764e32cfec3e27eca1
Reviewed-on: https://gerrit.libreoffice.org/10768
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>