fix: remove pip install statements (#1546)

because the tools are already installed in the docker image as of googleapis/testing-infra-docker#227
Source-Link: googleapis/synthtool@ab7384e
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-nodejs:latest@sha256:bb493bf01d28519e82ab61c490c20122c85a7119c03a978ad0c34b4239fbad15

Author: gcf-owl-bot[bot]

.github/.OwlBot.lock.yaml

@@ -13,5 +13,5 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-nodejs:latest
-  digest: sha256:b9e4584a1fe3c749e3c37c92497b13dce653b2e694f0261f0610eb0e15941357
-# created: 2022-05-05T21:08:42.530332893Z
+  digest: sha256:bb493bf01d28519e82ab61c490c20122c85a7119c03a978ad0c34b4239fbad15
+# created: 2022-08-23T18:40:55.597313991Z