fix: properly freeze Baggage object (#1508)

Author: intgr

sentry_sdk/tracing.py

@@ -279,7 +279,7 @@ def continue_from_headers(
 
         if sentrytrace_kwargs is not None:
             kwargs.update(sentrytrace_kwargs)
-            baggage.freeze
+            baggage.freeze()
 
         kwargs.update(extract_tracestate_data(headers.get("tracestate")))