chore: remove redundant words. (paritytech#4653)

remove redundant words in comments.

Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

substrate/primitives/storage/src/lib.rs

@@ -293,7 +293,7 @@ impl ChildInfo {
 		}
 	}
 
-	/// Return a the full location in the direct parent of
+	/// Return the full location in the direct parent of
 	/// this trie.
 	pub fn prefixed_storage_key(&self) -> PrefixedStorageKey {
 		match self {
@@ -302,7 +302,7 @@ impl ChildInfo {
 		}
 	}
 
-	/// Returns a the full location in the direct parent of
+	/// Returns the full location in the direct parent of
 	/// this trie.
 	pub fn into_prefixed_storage_key(self) -> PrefixedStorageKey {
 		match self {