chore: migrate to owl bot (#1387)

This PR migrates from autosynth to [owl-bot](https://github.com/googleapis/repo-automation-bots/tree/master/packages/owl-bot).

.github/.OwlBot.lock.yaml

@@ -0,0 +1,16 @@
+# Copyright 2021 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/repo-automation-bots/owlbot-python:latest
+  digest: sha256:c66ba3c8d7bc8566f47df841f98cd0097b28fff0b1864c86f5817f4c8c3e8600

.github/.OwlBot.yaml

@@ -0,0 +1,18 @@
+# Copyright 2021 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/repo-automation-bots/owlbot-python:latest
+
+begin-after-commit-hash: ee56c3493ec6aeb237ff515ecea949710944a20f