fdo#81592 Use 24-bit color depth, not 256 colors when converting an EPS-file.

This regression was introduced in f5c3f560.

Change-Id: Ica48732398cd5d225b433b177ff6e6fff649e732
Reviewed-on: https://gerrit.libreoffice.org/11268Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

filter/source/graphicfilter/ieps/ieps.cxx

@@ -379,7 +379,7 @@ static bool RenderAsBMPThroughGS(const sal_uInt8* pBuf, sal_uInt32 nBytesRead,
     OUString arg6("-dTextAlphaBits=4");
     OUString arg7("-dGraphicsAlphaBits=4");
     OUString arg8("-r300x300");
-    OUString arg9("-sDEVICE=bmp256");
+    OUString arg9("-sDEVICE=bmp16m");
     OUString arg10("-sOutputFile=-");
     OUString arg11("-");
     rtl_uString *args[] =