ci: use hashes in pip install statements in release.sh (googleapis#1484)

* ci: use hashes in pip install statements in release.sh

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

.github/.OwlBot.yaml

@@ -0,0 +1,18 @@
+# Copyright 2022 Google LLC
+#
+# 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.
+
+docker:
+  image: gcr.io/cloud-devrel-public-resources/owlbot-python:latest
+
+begin-after-commit-hash: 70f7f0525414fe4dfeb2fc2e81546b073f83a621

.kokoro/requirements.in

@@ -0,0 +1,8 @@
+gcp-docuploader
+gcp-releasetool
+importlib-metadata
+typing-extensions
+twine
+wheel
+setuptools
+nox