[classloads] add `replace` target to tests

Summary: The Makefile was missing that target and making `make test-replace` at the root of the repo fail.

Reviewed By: ngorogiannis

Differential Revision: D13990483

fbshipit-source-id: 805b5d2a9

infer/tests/codetoanalyze/java/classloads/Makefile

@@ -60,3 +60,6 @@ test: loads.exp loads.exp.test
 	$(QUIET)cd $(TESTS_DIR) && \
 	$(call check_no_diff,$(TEST_REL_DIR)/loads.exp,$(TEST_REL_DIR)/loads.exp.test)
 
+.PHONY: replace
+replace:
+	@: