Remove G_PARAM_EXPLICIT_NOTIFY from the "opacity" property
Where it was added in d/p/clutter-Use-G_PARAM_EXPLICIT_NOTIFY-for-actor-and-stage-p.patch
Because it prevented listeners of 'notify::opacity' in gnome-shell from running, which caused the workspaces view to appear on top of the icon grid (LP: #1918874).
This partial revert is only needed for 3.38 where that gnome-shell code still exists. It is not needed in v40 onward where the affected gnome-shell code has been removed.