Revert "Alter guarantees provided by StatementList::toArray"

Author: thiemowmde

src/Statement/StatementList.php

@@ -237,10 +237,7 @@ public function getIterator() {
 	}
 
 	/**
-	 * Returns the wrapped array of statements. This retrieval operation is cheap.
-	 * No guarantees are given about the keys of the returned array.
-	 *
-	 * @return Statement[]
+	 * @return Statement[] Numerically indexed (non-sparse) array.
 	 */
 	public function toArray() {
 		return $this->statements;