Fix mehses -> meshes typo (bevyengine#16688)

# Objective

The "mehses" typo introduced in a review comment
[here](bevyengine#16657 (comment))
hurts my soul, it was merged right as I was about to comment about it :(

## Solution

Fix it :D

(also, why didn't the CI typo checker catch this?)

Author: Jondolf

crates/bevy_picking/src/mesh_picking/ray_cast/mod.rs

@@ -274,7 +274,7 @@ impl<'w, 's> MeshRayCast<'w, 's> {
                     return;
                 };
 
-                // Backfaces of 2d meshes are never culled, unlike 3d mehses.
+                // Backfaces of 2d meshes are never culled, unlike 3d meshes.
                 let backfaces = match (has_backfaces, mesh2d.is_some()) {
                     (false, false) => Backfaces::Cull,
                     _ => Backfaces::Include,