SLICC: Remove WakeUp* import calls from ast/__init__.py

I had recently committed a patch that removed the WakeUp*.py files from the
slicc/ast directory. I had forgotten to remove the import  calls for these
files from slicc/ast/__init__.py. This resulted in error while running
regressions on zizzer. This patch does the needful.

src/mem/slicc/ast/__init__.py

@@ -74,5 +74,3 @@ from slicc.ast.TypeFieldMemberAST import *
 from slicc.ast.TypeFieldMethodAST import *
 from slicc.ast.TypeFieldStateAST import *
 from slicc.ast.VarExprAST import *
-from slicc.ast.WakeUpAllDependentsStatementAST import *
-from slicc.ast.WakeUpDependentsStatementAST import *