Remove toolchain directive in go.mod

I don't really know why this wasn't failing previously, but it seems
necessary now to pass our validation step 

go.mod

@@ -2,8 +2,6 @@ module 0xacab.org/leap/obfsvpn
 
 go 1.22.2
 
-toolchain go1.22.2
-
 require (
 	0xacab.org/leap/menshen v0.0.0-20250313153840-1ef381b04b64
 	0xacab.org/leap/menshen-agent v0.0.0-20250313140933-8a982548c666