Checks REST API documentation: Fix heading level for 'Options' section

This section describes the query options that can be specified on some
of the REST endpoints, hence it shouldn't be a subsection of the
'JSON Entities' section which describes the JSON entities.

Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: I8c403cac9b1d74c5a50452f4fc2f5af8a2a0c886
diff --git a/src/main/resources/Documentation/rest-api-checks.md b/src/main/resources/Documentation/rest-api-checks.md
index 08fc979..3aeabef 100644
--- a/src/main/resources/Documentation/rest-api-checks.md
+++ b/src/main/resources/Documentation/rest-api-checks.md
@@ -192,7 +192,7 @@
 The `CheckState` enum can have the following values: `NOT_STARTED`, `FAILED`,
 `SCHEDULED`, `RUNNING`, `SUCCESSFUL` and `NOT_RELEVANT`.
 
-### <a id="query-options"> Options
+## <a id="query-options"> Options
 
 The following query options are supported in the `o` field of certain requests: