Base on MuirGlacier instead of Constantinople

This change was made most places, looks like only one was missing.

Author: carver

eth/vm/forks/berlin/__init__.py

@@ -3,8 +3,8 @@
 )
 
 from eth.rlp.blocks import BaseBlock
-from eth.vm.forks.constantinople import (
-    ConstantinopleVM,
+from eth.vm.forks import (
+    MuirGlacierVM,
 )
 from eth.vm.state import BaseState
 
@@ -17,7 +17,7 @@
 from .state import BerlinState
 
 
-class BerlinVM(ConstantinopleVM):
+class BerlinVM(MuirGlacierVM):
     # fork name
     fork = 'berlin'