Fix mesh flags (#15804)

Fixed incorrect mesh flags offsets

## Testing

Ran OIT example since that was the affected flag

Author: ecoskey

crates/bevy_pbr/src/render/mesh.rs

@@ -1494,8 +1494,8 @@ bitflags::bitflags! {
         const SCREEN_SPACE_REFLECTIONS          = 1 << 16;
         const HAS_PREVIOUS_SKIN                 = 1 << 17;
         const HAS_PREVIOUS_MORPH                = 1 << 18;
-        const OIT_ENABLED                       = 1 << 18;
-        const LAST_FLAG                         = Self::HAS_PREVIOUS_MORPH.bits();
+        const OIT_ENABLED                       = 1 << 19;
+        const LAST_FLAG                         = Self::OIT_ENABLED.bits();
 
         // Bitfields
         const MSAA_RESERVED_BITS                = Self::MSAA_MASK_BITS << Self::MSAA_SHIFT_BITS;