fix typo

src/Index/AliasProcessor.php

@@ -180,7 +180,7 @@ private function getAliasedIndex(Client $client, string $aliasName): ?string
         }
 
         if (\count($aliasedIndexes) > 1) {
-            throw new \RuntimeException(\sprintf('Alias "%s" is used for multiple indexes: ["%s"]. Make sure it\'seither not used or is assigned to one index only', $aliasName, \implode('", "', $aliasedIndexes)));
+            throw new \RuntimeException(\sprintf('Alias "%s" is used for multiple indexes: ["%s"]. Make sure it\'s either not used or is assigned to one index only', $aliasName, \implode('", "', $aliasedIndexes)));
         }
 
         return \array_shift($aliasedIndexes);