add note about prague timestamp

Author: gurukamath

src/ethereum/prague/__init__.py

@@ -4,4 +4,7 @@
 
 from ethereum.fork_criteria import ByTimestamp
 
+# TODO: Note that this is a dummy timestamp since the
+# timestamp for Prague is not finalised at the time of creating this PR.
+# The timestamp will have to be updated once Prague goes live.
 FORK_CRITERIA = ByTimestamp(1710338138)