add fixme note for unit conversion

compiler/base/wire_spice_model.py

@@ -18,6 +18,7 @@ class wire_spice_model():
     def cal_wire_c(self, wire_length, wire_width):
         from openram.tech import spice
         # Convert the F/um^2 to fF/um^2 then multiple by width and length
+        # FIXME: shouldn't it be 1e15?
         total_c = (spice["wire_unit_c"]*1e12) * wire_length * wire_width
         wire_c = total_c / self.lump_num
         return wire_c