Fix formatting error in documentation 'Program Abstraction' (#137)

Author: penguinfirst

Diff for: docs/en/program-abstraction.adoc

@@ -52,15 +52,15 @@ Exp -> Var | Literal | FieldAccess | ArrayAccess
 | StringLiteral | ClassLiteral | NullLiteral
 | MethodHandle | MethodType
 
-** FieldAccess -> InstanceFieldAccess | StaticFieldAccess
+* FieldAccess -> InstanceFieldAccess | StaticFieldAccess
 ** InstanceFieldAccess -> Var.FieldRef
 ** StaticFieldAccess -> FieldRef
 ** FieldRef -> <ClassType: Type FieldName>
 ** FieldName -> Identifier
 
 * ArrayAccess -> Var[Var]
 
-** NewExp -> NewInstance | NewArray | NewMultiArray
+* NewExp -> NewInstance | NewArray | NewMultiArray
 ** NewInstance -> _new_ ClassType
 ** NewArray -> _new_ Type[Var]
 ** NewMultiArray -> _new_ Type LengthList EmptyList