Remove TARGET_ANDROID_FILESYSTEM_CONFIG_H

TARGET_FS_CONFIG_GEN has existed as the preferred mechanism for two
releases, so we finally deprecate TARGET_ANDROID_FILESYSTEM_CONFIG_H.

Test: build
Change-Id: I299a4d1d1d893ac16d6e6ce2ec4659bfcdc19095
diff --git a/core/config.mk b/core/config.mk
index b02be03..71c3f68 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -91,6 +91,7 @@
   GLOBAL_CFLAGS_NO_OVERRIDE GLOBAL_CPPFLAGS_NO_OVERRIDE \
   ,GCC support has been removed. Use Clang instead)
 $(KATI_obsolete_var DIST_DIR dist_goal,Use dist-for-goals instead. See $(CHANGES_URL)#dist)
+$(KATI_obsolete_var TARGET_ANDROID_FILESYSTEM_CONFIG_H,Use TARGET_FS_CONFIG_GEN instead)
 $(KATI_deprecated_var USER,Use BUILD_USERNAME instead. See $(CHANGES_URL)#USER)
 
 # This is marked as obsolete in envsetup.mk after reading the BoardConfig.mk