Use MAX associated const (#9196)

* Use MAX associated const

substrate/frame/system/src/lib.rs

@@ -778,7 +778,7 @@ fn hash69<T: AsMut<[u8]> + Default>() -> T {
 /// This type alias represents an index of an event.
 ///
 /// We use `u32` here because this index is used as index for `Events<T>`
-/// which can't contain more than `u32::max_value()` items.
+/// which can't contain more than `u32::MAX` items.
 type EventIndex = u32;
 
 /// Type used to encode the number of references an account has.