Fix: delete Cairo 2 contracts when running make clean (lambdaclass#1579)

* Fix: delete Cairo 2 contracts when running make clean

The .casm files in `cairo_programs/cairo-2-contracts` were not deleted
in the `clean` target, resulting in errors when bisecting / testing
older versions.

* add sierra files

Makefile

@@ -319,6 +319,8 @@ clean:
 	rm -f $(PRINT_TEST_DIR)/*.json
 	rm -f $(CAIRO_1_CONTRACTS_TEST_DIR)/*.sierra
 	rm -f $(CAIRO_1_CONTRACTS_TEST_DIR)/*.casm
+	rm -f $(CAIRO_2_CONTRACTS_TEST_DIR)/*.sierra
+	rm -f $(CAIRO_2_CONTRACTS_TEST_DIR)/*.casm
 	rm -f $(TEST_PROOF_DIR)/*.json
 	rm -f $(TEST_PROOF_DIR)/*.memory
 	rm -f $(TEST_PROOF_DIR)/*.trace