Remove dependency on imagemagick

djvulibre fails only on OBS with the error,

[  196s] convert: delegate failed `'rsvg-convert' -o '%o' '%i'' @ error/delegate.c/InvokeDelegate/1966.
[  196s] convert: unable to open file `/tmp/magick-iZFT0Lkx4IIkazqT8-5nRDu2BTtadFa1': No such file or directory @ error/constitute.c/ReadImage/614.
[  196s] convert: no images defined `22x22/mimetypes/image-vnd.djvu.png' @ error/convert.c/ConvertImageCommand/3229.
[  196s] convert: delegate failed `'rsvg-convert' -o '%o' '%i'' @ error/delegate.c/InvokeDelegate/1966.
[  196s] convert: unable to open file `/tmp/magick-veU6vGPreqaMLh3UMXmE4tR23lt6ITNG': No such file or directory @ error/constitute.c/ReadImage/614.
[  196s] convert: no images defined `16x16/mimetypes/image-vnd.djvu.png' @ error/convert.c/ConvertImageCommand/3229.

If build depends has librsvg2-bin | imagemagick, the configure does not locate rsvg-convert,

checking for rsvg-convert... false

When imagemagick is removed the below message is seen,

checking for rsvg-convert... /usr/bin/rsvg-convert

To fix the build error with djvulibre, remove the dependency on ImageMagick and rely solely on librsvg2-bin, which will enable the build process to locate rsvg-convert without any issues.

https://phabricator.apertis.org/T9521