Skip installing git in build_bundle CI step (#1564)

`create-bundle` [used to depend on
git](https://github.com/tiny-pilot/tinypilot/blob/1.8.0/bundler/create-bundle),
as it downloaded external roles using git and used `git` to pull version
information about the local repo.

We've since simplified the bundle build process, so we no longer require
git, and we can delete the CI step when we install git into the
container. This saves us about 5s on every bundle build in CI.

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.circleci/continue_config.yml

@@ -252,9 +252,6 @@ jobs:
       - checkout
       - attach_workspace:
           at: ./bundler/bundle/
-      - run:
-          name: Install dependencies
-          command: sudo apt-get update && sudo apt-get install -y git
       - run:
           name: Create the bundle
           command: ./bundler/create-bundle