Update rules.mk

Bug: 281857510
Change-Id: I03ed49070929cb41e5681bc1c37f832257e9cf84
diff --git a/rules.mk b/rules.mk
index 833c536..a78891e 100644
--- a/rules.mk
+++ b/rules.mk
@@ -1,4 +1,4 @@
-# This file is generated by cargo2rulesmk.py --run --config cargo2rulesmk.json --features .
+# This file is generated by cargo2rulesmk.py --run --config cargo2rulesmk.json.
 # Do not modify this file as changes will be overridden on upgrade.
 
 LOCAL_DIR := $(GET_LOCAL_DIR)
@@ -7,7 +7,7 @@
 MODULE_SRCS := \
 	$(LOCAL_DIR)/src/lib.rs \
 
-MODULE_RUST_EDITION := 2018
+MODULE_RUST_EDITION := 2021
 MODULE_RUSTFLAGS += \
 	--cfg 'feature="alloc"' \
 	--cfg 'feature="zeroize_derive"' \