Drop level of heading for vendor extensions

doc/mavlink_gitbook.py

@@ -39,7 +39,7 @@
 index_text+='\n# Message Definitions'
 index_text+='\n\nMAVLink messages are defined in XML files in the [mavlink/message definitions](https://github.com/mavlink/mavlink/blob/master/message_definitions/) folder. The messages that are common to all systems are defined in [common.xml](https://github.com/mavlink/mavlink/blob/master/message_definitions/v1.0/common.xml) (only messages contained in this file are considered standard messages).'
 index_text+='\n\nThe common messages are provided as human-readable tables in: [Common](../messages/common.md).'
-index_text+='\n\n# Vendor Specific Extensions (Dialects) {#dialects}'
+index_text+='\n\n## Vendor Specific Extensions (Dialects) {#dialects}'
 index_text+='\n\nMAVLink protocol-specific and vendor-specific messages (dialects) are stored in separate XML files. These often extend (include) the [common](../messages/common.md) messages.'
 index_text+='\n\n> **Note** Vendor forks of MAVLink may contain messages that are not yet merged, and hence will not appear in this documentation.'
 index_text+='\n\nThe human-readable forms of the vendor XML files are linked below:'