debian: Remove ImageMagick patch; an equivalent patch now exists in next

If a user wanted to build a Debian package from the next branch, then
it would fail immediately when quilt tried to apply the patches.

debian/patches/10_support_imagemagick6.diff

@@ -1,27 +0,0 @@
-Description: Restore support for ImageMagick v6, as v7 not in Debian.
-Origin: https://repo.or.cz/wmaker-crm.git/commitdiff/1dace56 (reversed)
-Bug-Debian: https://bugs.debian.org/929825
-Last-Update: 2020-04-05
-
---- a/m4/wm_imgfmt_check.m4
-+++ b/m4/wm_imgfmt_check.m4
-@@ -312,7 +312,7 @@
-               dnl
-               dnl The library was found, check if header is available and compiles
-               wm_save_CFLAGS="$CFLAGS"
--              AS_IF([wm_fn_lib_try_compile "MagickWand/MagickWand.h" "MagickWand *wand;" "wand = NewMagickWand()" "$wm_cv_libchk_magick_cflags"],
-+              AS_IF([wm_fn_lib_try_compile "wand/magick_wand.h" "MagickWand *wand;" "wand = NewMagickWand()" "$wm_cv_libchk_magick_cflags"],
-                   [wm_cv_libchk_magick="$wm_cv_libchk_magick_cflags % $wm_cv_libchk_magick_libs"],
-                   [AC_MSG_ERROR([found MagickWand library but could not compile its header])])
-               CFLAGS="$wm_save_CFLAGS"])dnl
---- a/wrlib/load_magick.c
-+++ b/wrlib/load_magick.c
-@@ -22,7 +22,7 @@
- 
- #include "config.h"
- 
--#include <MagickWand/MagickWand.h>
-+#include <wand/MagickWand.h>
- 
- #include "wraster.h"
- #include "imgformat.h"

debian/patches/series

@@ -1,3 +1,2 @@
-10_support_imagemagick6.diff
 53_Debian_WMState.diff
 75_WPrefs_to_bindir_when_gnustedir_is_set.diff