Fix typo

Author: Richard Taylor

REFERENCE.md

@@ -38,7 +38,7 @@ void setProceedOnNetworkFail(boolean proceed)
 
 Note that this should be used with *CAUTION* because it may allow a connection to be established before any dynamic pins have been received via Approov, thus potentially opening the channel to a MitM.
 
-### SetDevKey
+## SetDevKey
 [Sets a development key](https://approov.io/docs/latest/approov-usage-documentation/#using-a-development-key) in order to force an app to be passed. This can be used if the app has to be resigned in a test environment and would thus fail attestation otherwise.
 
 ```Java