exec source has left-over event_per_line configuration in documentation

[bruceg]

PR #9337 (enhancement(codecs, exec source): Integrate Decoder/DecodingConfig with exec source) added the framing and decoding configuration items to the exec source and dropped the event_per_line setting. However, the documentation was not updated to match (and no mention was given in the upgrade guide). This needs to be corrected in the documentation.