gst_all_1.gst-plugins-bad: disable asserts

`lib/gstreamer-1.0/libgstdvbsubenc.so` and `lib/libgstcodecparsers-1.0.so` include `${gstreamer.dev}/include/gstreamer-1.0/gst/base/gstbitwriter.h` in their .rodata section, increasing the runtime closure unnecessarily. This happens because `gstbitwriter.h` header uses GLib’s `g_assert` macro, which wants to print `__FILE__` on assertion failure.

The assertions can and should be disabled on stable releases (https://gitlab.freedesktop.org/gstreamer/gstreamer/-/commit/7b8d74c15bb817c65c06c63580dae3633a914841) so let’s do that.

pkgs/development/libraries/gstreamer/bad/default.nix

···
   mesonFlags = [
     "-Dexamples=disabled" # requires many dependencies and probably not useful for our users
     "-Ddoc=disabled" # `hotdoc` not packaged in nixpkgs as of writing
+    "-Dglib-asserts=disabled" # asserts should be disabled on stable releases
 
     "-Davtp=disabled"
     "-Ddts=disabled" # required `libdca` library not packaged in nixpkgs as of writing, and marked as "BIG FAT WARNING: libdca is still in early development"