Update MEC012.md - STF 599 update (formatting clean-up)

| subscriptions/NrMeasRepUeSubscription <br><br>_Notification providing New Radio (NR) UE measurement reports (5G), when available_ <br><br> _New STF599_| Notification reports 5G NR UE measurements, including:  <ul><li> associateId: UE's IPV4 address <li> NR trigger: NR_PERIODICAL <li> 5G serving cell information: <ul><li> NR Cell Id <li> SSB reference signal received power <li> SSB reference signal received quality </ul> <li> Best neighbor cell info: <ul><li> SSB rsrp <li> SSB rsrq </li></ul> <li> 5G NR neighbor cell info list:  <ul><li> NR cell id <li> SSB rsrp <li> SSB rsrq </li></ul> <li> 4G neighbor cell info list:  <ul><li> 4G egci cell id <li> rsrp <li> rsrq </li></ul> </ul> <br> Supported filters (filterCriteriaNrMrs) include: <ul><li> associateId list: UE IPv4 address (if missing all UEs) <li> nrcgi: list of cells (filters for specific cells; if not present, measurements on any serving cell) <li> trigger: ignored (only NR periodic) <li> expiry deadline:  ignored </ul> | As a Sandbox user, I can set notifications to monitor UE measurements from connected 5G NR cells that include:  NR serving cell id, serving cell signal levels, and neighbor cells (4G and 5G). <br><br> _Sandbox supports periodic events (e.g. NR_PERIODICAL). Sandbox triggers reports based on an internal period of 1 second (which is not MEC app or Sandbox user configurable)._ <br><br> _RNIS specification improvement may be to include notification frequency, duration, and max instance filter criteria._  |

| subscriptions/MeasTaSubscription <br><br>_Notification providing a UE timing advance report_ | _Not supporting - future consideration beyond STF599_ | Timing advanced can be emulated in the MEC Sandbox calculated based on terminal distance from a 4G PoA.  |

| subscriptions/CaReconfSubscription <br><br>_Carrier aggregation reconfiguration notification_ | _Not supporting - future consideration beyond STF599_ | Not supporting carrier aggregation emulation.  Too detailed for MEC Sandbox |

| subscriptions/S1BearerSubscription <br><br>_S1 bearer modification notification_ | _Not supporting - future consideration beyond STF599 | S1 Bearers are not modeled or emulated in the MEC Sandbox._ |

| subscriptions/S1BearerSubscription <br><br>_S1 bearer modification notification_ | _Not supporting - future consideration beyond STF599_ | S1 Bearers are not modeled or emulated in the MEC Sandbox. |