Remove outdated migration guide commands

Author: kegilbert

docs/tutorials/migrate-from-mbed-os-2-to-5.md

@@ -42,7 +42,6 @@ To update to Mbed OS 5 with the [Mbed CLI](../tools/developing-mbed-cli.html), r
 mbed import [URL of Project]
 cd [Project Name]
 mbed remove mbed
-mbed remove mbed-rtos
 mbed add mbed-os
 ```
 
@@ -89,7 +88,6 @@ In the command-line, run:
 mbed import https://os.mbed.com/teams/Seeed/code/Seeed_Grove_Buzzer/
 cd Seeed_Grove_Buzzer
 mbed remove mbed
-mbed remove mbed-rtos
 mbed add mbed-os
 mbed compile -m ublox_evk_odin_w2 -t gcc_arm
 ```
@@ -114,7 +112,6 @@ In the command-line, run:
 mbed import https://os.mbed.com/users/melse/code/SRF08HelloWorld/
 cd SRF08HelloWorld
 mbed remove mbed
-mbed remove mbed-rtos
 mbed add mbed-os
 mbed compile -m k64f -t gcc_arm
 ```
@@ -186,7 +183,6 @@ In the command-line, run:
 mbed import http://mbed.org/teams/AnalogDevices/code/CN0357-helloworld/
 cd CN0357-helloworld
 mbed remove mbed
-mbed remove mbed-rtos
 mbed add mbed-os
 mbed compile -m k64f -t gcc_arm
 ```