Remove redundant must_use and clarify doc

Author: Bluefinger

crates/bevy_ecs/src/entity/mod.rs

@@ -200,9 +200,8 @@ pub(crate) enum AllocAtWithoutReplacement {
 
 impl Entity {
     /// Construct an [`Entity`] from a raw `index` value and a non-zero `generation` value.
-    /// Ensure that the generation value is never greater than `0x3FFF_FFFF`.
+    /// Ensure that the masked generation value is never greater than `0x3FFF_FFFF`.
     #[inline(always)]
-    #[must_use]
     pub(crate) const fn from_raw_and_generation(index: u32, generation: NonZeroU32) -> Entity {
         Self { index, generation }
     }