remove unnecessary -- in config CLI commands

doc/platform_api/CMIS_and_C-CMIS_support_for_ZR.md

@@ -779,28 +779,29 @@ configure privisioning settings of the transceivers
 
 - Example (bring module up from low power mode, or bring down module to low power mode):
  ```
- admin@sonic:~# config interface transceiver lpmode Ethernet0 -- enable
+ admin@sonic:~# config interface transceiver lpmode Ethernet0 enable
  Enabling low-power mode for port Ethernet0 ... OK
 
- admin@sonic:~# config interface transceiver lpmode Ethernet0 -- disable
+ admin@sonic:~# config interface transceiver lpmode Ethernet0 disable
  Disabling low-power mode for port Ethernet0 ... OK
  ```
 
 - Example (config the privisioning frequency):
  ```
- admin@sonic:~# config interface transceiver frequency Ethernet0 -- 196025
+ admin@sonic:~# config interface transceiver frequency Ethernet0 196025
  Setting laser frequency to 196025 GHz on port Ethernet0
  ```
 
 - Example (config the privisioning TX power):
+The "--" is needed here because the provisioned value is negative.
  ```
  admin@sonic:~# config interface transceiver tx_power Ethernet0 -- -10.0
  Setting target Tx output power to -10.0 dBm on port Ethernet0
  ```
 
 - Example (config the loopback mode):
  ```
- admin@sonic:~$ config interface transceiver loopback Ethernet0 -- none
+ admin@sonic:~$ config interface transceiver loopback Ethernet0 none
  Setting loopback mode to none
  ```