gst_all_1.gst-plugins-good: disable asserts

`lib/gstreamer-1.0/libgstrtpmanager.so` includes `${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/ce64f0e0e0d4e692c8d99f9744d38b9676b3d720) so let’s do that.

pkgs/development/libraries/gstreamer/good/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
   ] ++ lib.optionals (!qt5Support) [
     "-Dqt5=disabled"
   ] ++ lib.optionals (!gtkSupport) [