[doc] Update Command-Reference.md, change "show bgp peer" command to "show bfd peer" (#2750)

Signed-off-by: PinghaoQu [email protected]
What I did
In the show bfd peer section, "show bgp peer" command should be "show bfd peer"
How I did it
Changed "show bgp peer" to "show bfd peer"
How to verify it
Check Command-Reference.md

Author: PinghaoQu

doc/Command-Reference.md

@@ -2049,7 +2049,7 @@ This command displays the state and key parameters of all BFD sessions that matc
 
 - Usage:
   ```
-  show bgp peer <peer-ip>
+  show bfd peer <peer-ip>
   ```
 - Example:
   ```