Avoid useless coercion checks in BytesNode when we already know that they do not apply.

Cython/Compiler/ExprNodes.py

@@ -1467,7 +1467,6 @@ class BytesNode(ConstNode):
         else:
             # not const => use plain C string literal and cast to mutable type
             literal = self.value.as_c_string_literal()
-            # C++ may require a cast
             result = typecast(self.type, PyrexTypes.c_void_ptr_type, literal)
         self.result_code = result