fix: remove pip install statements (#1546) (#653)

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

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
Co-authored-by: gcf-merge-on-green[bot] <60162190+gcf-merge-on-green[bot]@users.noreply.github.com>
Co-authored-by: losalex <90795544+losalex@users.noreply.github.com>

.github/.OwlBot.lock.yaml

@@ -15,3 +15,4 @@ docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-nodejs:latest
   digest: sha256:7fefeb9e517db2dd8c8202d9239ff6788d6852bc92dd3aac57a46059679ac9de
 # created: 2022-08-24T19:44:03.464675104Z
+