Fix indenting in table of contents
Fixes The "filter" section had the wrong header size, which
caused sections following it to have the wrong indentation in the
right-side table of contents.
@@ -40,7 +40,7 @@ docker 1.9, but kept around for backward compatibility.
Refer to [#17538](https://github.com/docker/docker/pull/17538) for further
information.
-## `filter` param for `/images/json` endpoint
+### `filter` param for `/images/json` endpoint
**Deprecated In Release: [v1.13.0](https://github.com/docker/docker/releases/tag/v1.13.0)**
**Target For Removal In Release: v17.12**
