Revert "Turn uses of `COVERAGE_PATHS` and `COVERAGE_EXCLUDE_PATHS` into errors."

This reverts commit ace5860719e5aac0ce59ad6f346b62db7c648647.

Reason for revert: Droidcop-triggered revert due to breakage https://android-build.googleplex.com/builds/quarterdeck?branch=git_rvc-dev-plus-aosp&target=build_test3&lkgb=6662220&lkbb=6662382&fkbb=6662228
Bug: 158212027
Bug: 160769227
Test: N/A revert
Change-Id: I0d366adcc735e9cc417d28013afb0386dea1fa64
diff --git a/core/main.mk b/core/main.mk
index 2a0d847..812cce0 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -102,14 +102,13 @@
 EMMA_INSTRUMENT := true
 endif
 
-# TODO(b/158212027): Remove this when we are certain these assertions are not
-# breaking any continuous build; then turn `COVERAGE_PATHS` and
-# `COVERAGE_EXCLUDE_PATHS` into kati obsolete variables.
+# TODO(b/158212027): Turn this into an error when all users have been moved to
+# `NATIVE_COVERAGE_PATHS` and `NATIVE_COVERAGE_EXCLUDE_PATHS`.
 ifneq ($(COVERAGE_PATHS),)
-  $(error Variable COVERAGE_PATHS is obsolete. Use NATIVE_COVERAGE_PATHS instead)
+  $(warning Variable COVERAGE_PATHS is deprecated. Please use NATIVE_COVERAGE_PATHS instead.)
 endif
 ifneq ($(COVERAGE_EXCLUDE_PATHS),)
-  $(error Variable COVERAGE_EXCLUDE_PATHS is obsolete. Use NATIVE_COVERAGE_EXCLUDE_PATHS instead)
+  $(warning Variable COVERAGE_EXCLUDE_PATHS is deprecated. Please use NATIVE_COVERAGE_EXCLUDE_PATHS instead.)
 endif
 
 ifeq (true,$(EMMA_INSTRUMENT))