meson: remove libass dirent patch

Handled more properly in libass itself

subprojects/libass.wrap

@@ -2,4 +2,3 @@
 directory = libass
 url = https://github.com/TypesettingTools/libass.git
 revision = meson-pr
-patch_directory = libass

subprojects/packagefiles/libass/dirent.h

@@ -1,6 +0,0 @@
-// libass uses dirent in a function we don't use, so just provide a dummy version
-typedef struct DIR { int dummy; } DIR;
-typedef struct dirent { char *d_name; } dirent;
-static inline DIR *opendir(const char *x) { return 0; }
-static inline struct dirent *readdir(DIR *x) { return 0; }
-static inline void closedir(DIR *x) { }