users can't run Quickstart docs in Cloud Code Shell until gcloud skaffold update version goes through.

### Expected behavior

Go to https://skaffold.dev/docs/quickstart/

> Click the "Open in Cloud Shell" Button

> Run `skaffold dev` to build and deploy your app continuously. You should see some outputs similar to the following entries:

> ```
> Listing files to watch...
> - skaffold-example
> Generating tags...
> - skaffold-example -> skaffold-example:v1.1.0-113-g4649f2c16
> Checking cache...
> - skaffold-example: Not found. Building
> Found [docker-desktop] context, using local docker daemon.
> Building [skaffold-example]...
> Sending build context to Docker daemon 3.072kB
> Step 1/6 : FROM golang:1.12.9-alpine3.10 as builder
> ---> e0d646523991
> Step 2/6 : COPY main.go .
> ---> Using cache
> ---> e4788ffa88e7
> Step 3/6 : RUN go build -o /app main.go
> ---> Using cache
> ---> 686396d9e9cc
> Step 4/6 : FROM alpine:3.10
> ---> 965ea09ff2eb
> Step 5/6 : CMD ["./app"]
> ---> Using cache
> ---> be0603b9d79e
> Step 6/6 : COPY --from=builder /app .
> ---> Using cache
> ---> c827aa5a4b12
> Successfully built c827aa5a4b12
> Successfully tagged skaffold-example:v1.1.0-113-g4649f2c16
> Tags used in deployment:
> - skaffold-example -> skaffold-example:c827aa5a4b12e707163842b803d666eda11b8ec20c7a480198960cfdcb251042
> local images can't be referenced by digest. They are tagged and referenced by a unique ID instead
> Starting deploy...
> - pod/getting-started created
> Watching for changes...
> [getting-started] Hello world!
> [getting-started] Hello world!
> [getting-started] Hello world!
> ```

### Actual behavior

```
alex@cloudshell:~/cloudshell_open/skaffold/examples/getting-started$ skaffold dev
parsing skaffold config: unknown api version: "skaffold/v2beta12"
```

### Information

- Skaffold version: `v1.19.0`
- Operating system: Google Cloud Shell
- Contents of skaffold.yaml:
```yaml
apiVersion: skaffold/v2beta12
kind: Config
build:
artifacts:
- image: skaffold-example
deploy:
kubectl:
manifests:
- k8s-*
```

### Steps to reproduce the behavior

1. Go to https://skaffold.dev/docs/quickstart/
2. Click the "Open in Cloud Shell" Button
3. Run `skaffold dev`