Update to import vhal_const_2_0 as vhal_const_2_1 is gone

Bug: 66915780
Test: Manual test by running scripts locally with a connected device
Change-Id: I46b4e24d37fce6efbb1be5dbb5edd1f051bd874d
diff --git a/tools/emulator/gui.py b/tools/emulator/gui.py
index 594526a..3a0161d 100755
--- a/tools/emulator/gui.py
+++ b/tools/emulator/gui.py
@@ -24,7 +24,7 @@
 
 import VehicleHalProto_pb2
 from vhal_emulator import Vhal
-import vhal_consts_2_1 as c
+import vhal_consts_2_0 as c
 
 
 # Define a simple thread that receives messages from a vhal object (v) and prints them