Change timestamp to -stubs.srcjar

Test: m clean && m -j docs
Bug: b/70351683

Change-Id: Id036e203bbfd81a9a3c089f21d0832495027447a
Merged-In: Id036e203bbfd81a9a3c089f21d0832495027447a
diff --git a/core/apidiff.mk b/core/apidiff.mk
index 7876c11..23da624 100644
--- a/core/apidiff.mk
+++ b/core/apidiff.mk
@@ -124,7 +124,7 @@
 		$(full_java_lib_deps) \
 		$(jdiff) \
 		$(doclava) \
-		$(call doc-timestamp-for,$(LOCAL_MODULE)) \
+		$(OUT_DOCS)/$(LOCAL_MODULE)-docs-stubs.srcjar \
 		$(LOCAL_ADDITIONAL_DEPENDENCIES)
 	@echo Generating API diff: $(PRIVATE_OUT_DIR)
 	@echo   Old API: $(PRIVATE_OLDAPI)