Re-landing "removing gsi_keys.mk"

It's no longer required to install the compliance GSI
public keys into the ramdisk. Those public keys just need
to be included in the VTS test suite for GSI verification.

Bug: 176869478
Test: TreeHugger
Change-Id: I3714de75b94be43a1364b89b92d893b336aa014b

target/product/gsi_keys.mk

@@ -1,22 +0,0 @@
-#
-# Copyright (C) 2019 The Android Open-Source Project
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#      http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-#
-
-# Include GSI keys into first-stage ramdisk, so we can enable verified
-# boot when booting a GSI.
-PRODUCT_PACKAGES += \
-    q-gsi.avbpubkey \
-    r-gsi.avbpubkey \
-    s-gsi.avbpubkey \