UI: Fix Symmetry options in weight paint panels

The now redundant "X" checkbox is removed since it's also present in the
Symmetry panel above. The Topology Mirror is moved into the Symmetry
panel also.

This was needed because `Mesh.use_x_mirror` has recently been turned into
different functionality, and its old functionality now lives under
`Mesh.use_mirror_vertex_group_x`. Something went wrong in the UI in This
transition.

Differential Revision: https://developer.blender.org/D9287

release/scripts/startup/bl_ui/space_view3d_toolbar.py

@@ -957,12 +957,16 @@ class VIEW3D_PT_tools_weightpaint_symmetry(Panel, View3DPaintPanel):
         layout = self.layout
         tool_settings = context.tool_settings
         wpaint = tool_settings.weight_paint
-        draw_vpaint_symmetry(layout, wpaint, context.object.data)
+        mesh = context.object.data
+        draw_vpaint_symmetry(layout, wpaint, mesh)
 
         col = layout.column()
         row = col.row(align=True)
-        row.prop(context.object.data, 'use_mirror_vertex_group_x')
+        row.prop(mesh, 'use_mirror_vertex_group_x')
 
+        row = layout.row(align=True)
+        row.active = mesh.use_mirror_vertex_group_x
+        row.prop(mesh, "use_mirror_topology")
 
 class VIEW3D_PT_tools_weightpaint_symmetry_for_topbar(Panel):
     bl_space_type = 'TOPBAR'
@@ -995,14 +999,6 @@ class VIEW3D_PT_tools_weightpaint_options(Panel, View3DPaintPanel):
 
         col.prop(wpaint, "use_group_restrict")
 
-        obj = context.weight_paint_object
-        if obj.type == 'MESH':
-            mesh = obj.data
-            col.prop(mesh, "use_mirror_x")
-            row = col.row()
-            row.active = mesh.use_mirror_x
-            row.prop(mesh, "use_mirror_topology")
-
 
 # ********** default tools for vertex-paint ****************