Fix docs (#7710)

* fix docs

* Update frame/merkle-mountain-range/src/lib.rs

Co-authored-by: Alexander Theißen <[email protected]>

Co-authored-by: Alexander Theißen <[email protected]>

Author: gui1117

src/traits.rs

@@ -1901,7 +1901,7 @@ impl PalletVersion {
 
 	/// Returns the storage key for a pallet version.
 	///
-	/// See [`PALLET_VERSION_STORAGE_KEY_POSTIFX`] on how this key is built.
+	/// See [`PALLET_VERSION_STORAGE_KEY_POSTFIX`] on how this key is built.
 	///
 	/// Returns `None` if the given `PI` returned a `None` as name for the given
 	/// `Pallet`.