doc: update example output

Author: samedii

README.md

@@ -50,6 +50,7 @@ exports
     "updated": "2024-02-01T23:20:20.605136+00:00",
     "id": "461731a1-96c8-4ed6-99e4-9fe424eb9c40",
     "measurement_name": "20231001_124327_2011T",
+    "measured": "2023-10-01T12:43:27.605136+00:00",
     "type": "fastenings",
     "downloaded": null,
     "created": "2024-02-01T23:20:20.605136+00:00",
@@ -61,7 +62,6 @@ exports
 export_data
 
 ```json
-{"export_datetime": "2024-02-04T21:21:12.866787", "measurement": "20231001_124327_2011T"}
 {"id": "56fb582a-0280-43fa-81f3-2a444e7e4273", "position_geographical": {"track_section": "111",
 ...
 ```