UI: Fix typo "subdivion" -> subdivision

In the Multires panel, use singular Subdivision instead of Subdivisions.

source/blender/blenkernel/intern/subdiv_deform.c

@@ -214,7 +214,7 @@ void BKE_subdiv_deform_coarse_vertices(struct Subdiv *subdiv,
     }
   }
 
-  /* Initialize subdivion mesh creation context. */
+  /* Initialize subdivision mesh creation context. */
   SubdivDeformContext subdiv_context = {0};
   subdiv_context.coarse_mesh = coarse_mesh;
   subdiv_context.subdiv = subdiv;

source/blender/blenkernel/intern/subdiv_foreach.c

@@ -1746,7 +1746,7 @@ static void subdiv_foreach_vertices_of_loose_edges_task(void *__restrict userdat
   const int num_subdiv_vertices_per_coarse_edge = resolution - 2;
   const Mesh *coarse_mesh = ctx->coarse_mesh;
   const MEdge *coarse_edge = &coarse_mesh->medge[coarse_edge_index];
-  /* Subdivion vertices which corresponds to edge's v1 and v2. */
+  /* Subdivision vertices which corresponds to edge's v1 and v2. */
   const int subdiv_v1_index = ctx->vertices_corner_offset + coarse_edge->v1;
   const int subdiv_v2_index = ctx->vertices_corner_offset + coarse_edge->v2;
   /* First subdivided inner vertex of the edge.  */

source/blender/blenkernel/intern/subdiv_mesh.c

@@ -1207,7 +1207,7 @@ Mesh *BKE_subdiv_to_mesh(Subdiv *subdiv,
       return NULL;
     }
   }
-  /* Initialize subdivion mesh creation context. */
+  /* Initialize subdivision mesh creation context. */
   SubdivMeshContext subdiv_context = {0};
   subdiv_context.settings = settings;
   subdiv_context.coarse_mesh = coarse_mesh;

source/blender/modifiers/intern/MOD_multires.c

@@ -487,7 +487,7 @@ static void panelRegister(ARegionType *region_type)
 {
   PanelType *panel_type = modifier_panel_register(region_type, eModifierType_Multires, panel_draw);
   modifier_subpanel_register(
-      region_type, "subdivide", "Subdivions", NULL, subdivisions_panel_draw, panel_type);
+      region_type, "subdivide", "Subdivision", NULL, subdivisions_panel_draw, panel_type);
   modifier_subpanel_register(region_type, "shape", "Shape", NULL, shape_panel_draw, panel_type);
   modifier_subpanel_register(
       region_type, "generate", "Generate", NULL, generate_panel_draw, panel_type);