ref(python): Clarify that continue_trace does not start a transaction (#11315)

Author: sentrivana

platform-includes/distributed-tracing/custom-instrumentation/python.mdx

@@ -18,13 +18,18 @@ from my_project import get_incoming_headers_as_dict
 
 headers = get_incoming_headers_as_dict()
 
-sentry_sdk.continue_trace(headers)
+transaction = sentry_sdk.continue_trace(headers)
+with sentry_sdk.start_transaction(transaction):
+   ...
 ```
 
 In this example, `get_incoming_headers_as_dict()` returns a dictionary that contains tracing information from HTTP headers, environment variables, or any other mechanism your project uses to communicate with the outside world.
 
 Sentry's `continue_trace()` function will extract the given headers, try to find the `sentry-trace` and `baggage` headers, and store them in memory for later use.
 
+`continue_trace()` returns a transaction, but does not start it. To start the transaction, use `start_transaction()`.
+
+
 ## 2. Inject Tracing Information to Outgoing Requests
 
 For distributed tracing to work, the two headers `sentry-trace` and `baggage`, must be added to outgoing requests. If you pregenerate HTML on the server-side, you might want to take a look at [Inject Tracing Information into Rendered HTML](#inject-tracing-information-into-rendered-html), which describes how to pass on tracing information through HTML meta tags.