Fix Open Telemetry framework example (#653)

The `hex` function does not format the trace and span id correctly.  In as much as the spec [says](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/api.md#retrieving-the-traceid-and-spanid) the span-id and trace-id are fixed with hex numbers. 16 chars for the span-id and 32 for the trace-id.

docs/frameworks.md

@@ -89,9 +89,9 @@ def add_open_telemetry_spans(_, __, event_dict):
     parent = getattr(span, "parent", None)
 
     event_dict["span"] = {
-        "span_id": hex(ctx.span_id),
-        "trace_id": hex(ctx.trace_id),
-        "parent_span_id": None if not parent else hex(parent.span_id),
+        "span_id": format(ctx.span_id, "016x"),
+        "trace_id": format(ctx.trace_id, "032x"),
+        "parent_span_id": None if not parent else format(parent.span_id, "016x"),
     }
 
     return event_dict