To fix the stp clear cli syntax error

[twtseng-tim]

What I did

The command syntax was modified to resolve the STP clear CLI error.

How I did it

How to verify it

admin@as9726-32d-1:~$ sudo sonic-clear spanning-tree statistics
All stats cleared
admin@as9726-32d-1:~$ sudo sonic-clear spanning-tree statistics interface Ethernet0
Stats cleared for Ethernet0
admin@as9726-32d-1:~$ sudo sonic-clear spanning-tree statistics vlan 1000
Stats cleared for VLAN 1000
admin@as9726-32d-1:~$ sudo sonic-clear spanning-tree statistics vlan-interface 1000 Ethernet8
Stats cleared for VLAN 1000 Ethernet8

Previous command output (if the output of a command-line utility has changed)

New command output (if the output of a command-line utility has changed)