Copied from https://gitlab.freedesktop.org//gstreamer/gst-plugins-bad/-/merge_requests/2545
tests/check/meson.build uses the openjpeg_dep variable unconditionally, and the subdir_done() is useless anyway, since the plugin is only built if openjpeg_dep.found() is true. Fixes:
..\tests\check\meson.build:23:0: ERROR: Unknown variable "openjpeg_dep".
In particular, this fixes the build on UWP since we disable openjpeg explicitly in Cerbero when building for UWP.