Doc: Fix asciidoctor warning

WARNING: dev-plugins.txt.html_htmlonly_expn: line 873: section title out of sequence: expected level 2, got level 3

Change-Id: Ic3604cb1bed8c23948115fb2f18f28145cb18607
diff --git a/Documentation/dev-plugins.txt b/Documentation/dev-plugins.txt
index 383f5c0..1cad9c1 100644
--- a/Documentation/dev-plugins.txt
+++ b/Documentation/dev-plugins.txt
@@ -870,7 +870,7 @@
 [[query_attributes]]
 == Change Attributes
 
-==== ChangePluginDefinedInfoFactory
+=== ChangePluginDefinedInfoFactory
 
 Plugins can provide additional attributes to be returned from the Get Change and
 Query Change APIs by implementing the `ChangePluginDefinedInfoFactory` interface
@@ -977,7 +977,7 @@
 Runtime exceptions generated by the implementors of ChangePluginDefinedInfoFactory
 are encapsulated in PluginDefinedInfo objects which are part of SSH/REST query output.
 
-==== ChangeAttributeFactory
+=== ChangeAttributeFactory
 
 Alternatively, there is also `ChangeAttributeFactory` which takes in one single
 `ChangeData` at a time. `ChangePluginDefinedInfoFactory` should be preferred