Changes database engineer to just engineer

Rectifies Database Query Comments guide to just use Engineer instead of
DB engineer, as we don't have those on call

doc/development/database_query_comments.md

@@ -6,7 +6,7 @@ queries generated by ActiveRecord.
 
 It is very useful for tracing problematic queries back to the application source.
 
-A DB Engineer during an on-call incident will have the full context of a query
+An engineer during an on-call incident will have the full context of a query
 and its application source from the comments.
 
 ## Metadata information in comments