Add qvm-firewall reset action to the man page

QubesOS/qubes-issues#4710

doc/manpages/qvm-firewall.rst

@@ -12,6 +12,8 @@ Synopsis
 
 :command:`qvm-firewall` [-h] [--verbose] [--quiet] [--reload] *VMNAME* list [--raw]
 
+:command:`qvm-firewall` [-h] [--verbose] [--quiet] [--reload] *VMNAME* reset
+
 Options
 -------
 
@@ -48,6 +50,8 @@ Available actions:
 
 * list - list all the rules for a given VM.
 
+* reset - remove all firewall rules and reset to default (accept all connections)
+
 
 Rule syntax
 -----------