docs: Standardize documentation headings (remove multiple # H1)

- Remove multiple single top-level (# H1) headings per file
 - Use (# H2 and ###### H6) sub-headings for consistency
 - Remove any trailing # in the headings
 - This ensures proper table of contents rendering in MkDocs.

 - Also removed RUN_NR_multiple_BWPs.md as it is moved to MAC usage

doc/NR_SA_Tutorial_OAI_multi_UE.md

@@ -16,10 +16,10 @@
 
 [[_TOC_]]
 
-# Scenario
+## Scenario
 This tutorial is about how to configure and run multiple OAI nrUE in the same end-to-end OAI 5G setup with RFsimulator.
 
-# Pre-requisites
+## Pre-requisites
 
 This tutorial is assuming that OAI CN5G and OAI RAN are already deployed. To learn how to deploy and run a basic setup with OAI nrUE, please refer to [NR_SA_Tutorial_OAI_nrUE.md](NR_SA_Tutorial_OAI_nrUE.md).
 
@@ -29,9 +29,9 @@ Also, it is suggested to get some knowledge on how the channel simulation with O
 - Channel simulation with OAI [channel_simulation.md](../openair1/SIMULATION/TOOLS/DOC/channel_simulation.md)
 - Telnet server usage [telnetusage.md](../common/utils/telnetsrv/DOC/telnetusage.md).
 
-# Run multiple UEs in RFsimulator
+## Run multiple UEs in RFsimulator
 
-## Multiple nrUEs with namespaces
+### Multiple nrUEs with namespaces
 
 Important notes:
 
@@ -69,7 +69,7 @@ Important notes:
 
 in the command above, please note that the IMSI and the telnet port changed.
 
-## Running Multiple UEs with Docker
+### Running Multiple UEs with Docker
 
 1. Make sure OAI nrUE image is pulled:
 
@@ -110,7 +110,7 @@ in the command above, please note that the IMSI and the telnet port changed.
    docker compose down -v
    ```
 
-# Further reading
+## Further reading
 
 For more details and scenarios, refer to the following files: