Fix T88188: Keyframing Vertex Mass in Cloth Simulation doesn't have any

effect

The way it is now, `ClothVertex->mass` is setup once for the clothObject
and then reused if it already exists [so does not change across frames/
steps] which happens in`cloth_from_object` / `do_init_cloth`, where
`SIM_cloth_solver_init` / `SIM_mass_spring_set_vertex_mass` are called
and set up masses in `Implicit_Data`.

Seems possible to update `ClothVertex->mass` every step in
`do_step_cloth`, however it seems more involved to update the masses in
`Implicit_Data` there as well. The masses from `Implicit_Data` are
accessed in many places, so it would be mandatory to have these masses
kept up-to-date (and even then it is unclear if the solver was designed
to work with these animated or if there are assumptions about this being
stable across the sim).

So propose to remove the (broken/not implemented) animation capabilities
on the property instead.

Maniphest Tasks: T88188

Differential Revision: https://developer.blender.org/D11225

source/blender/makesrna/intern/rna_cloth.c

@@ -652,6 +652,7 @@ static void rna_def_cloth_sim_settings(BlenderRNA *brna)
   prop = RNA_def_property(srna, "mass", PROP_FLOAT, PROP_UNIT_MASS);
   RNA_def_property_range(prop, 0.0f, FLT_MAX);
   RNA_def_property_ui_text(prop, "Vertex Mass", "The mass of each vertex on the cloth material");
+  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
   RNA_def_property_update(prop, 0, "rna_cloth_update");
 
   prop = RNA_def_property(srna, "vertex_group_mass", PROP_STRING, PROP_NONE);