package/imagemagick: security bump to version 7.10.51

package/imagemagick: security bump to version 7.10.51

- Fix CVE-2020-29599: ImageMagick before 6.9.11-40 and 7.x before
  7.0.10-40 mishandles the -authenticate option, which allows setting a
  password for password-protected PDF files. The user-controlled password
  was not properly escaped/sanitized and it was therefore possible to
  inject additional shell commands via coders/pdf.c.
- Update license hash (correct wording to match Apache 2 license:
  https://github.com/ImageMagick/ImageMagick/commit/45e5d2493c08e7cb49f7268c01d847e88f78fd6c)

https://github.com/ImageMagick/ImageMagick/blob/7.0.10-51/ChangeLog

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>