message: Fix typo in api core documentation
diff: @@ -400,7 +400,7 @@ Since the [`client.executeQuery`](#clientexecutequery) and other execute methods
  [`client.query`](#clientquery) and [`client.mutation`](#clientmutation) methods use this helper as
  well to create requests.
  -The helper takes are of creating a unique `key` for the `GraphQLRequest`. This is a hash of the
  +The helper takes care of creating a unique `key` for the `GraphQLRequest`. This is a hash of the
  `query` and `variables` if they're passed. The `variables` will be stringified using
  [`stringifyVariables`](#stringifyvariables), which outputs a stable JSON string.
  