fix datasource api docs

reflects change in e2f6633d

docs/sources/reference/http_api.md

@@ -183,7 +183,7 @@ Status Codes:
 
 ### Create data source
 
-`PUT /api/datasources`
+`POST /api/datasources`
 
 **Example Response**:
 
@@ -192,9 +192,9 @@ Status Codes:
 
         {"message":"Datasource added"}
 
-### Edit an existing data source
+### Update an existing data source
 
-`POST /api/datasources`
+`PUT /api/datasources/:datasourceId`
 
 ### Delete an existing data source