updated to ONLY_SCALE_OUT

[edwardmedia]

Fixes hashicorp/terraform-provider-google#15879

Release Note Template for Downstream PRs (will be copied)

compute: updated the `autoscaling_policy.mode` to accept `ONLY_SCALE_OUT` on `google_compute_autoscaler` 

[edwardmedia]

reference https://cloud.google.com/compute/docs/reference/rest/v1/autoscalers

[modular-magician]

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[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

Terraform GA: Diff ( 4 files changed, 6 insertions(+), 6 deletions(-))
Terraform Beta: Diff ( 4 files changed, 6 insertions(+), 6 deletions(-))

[modular-magician]

Tests analytics

Total tests: 3062
Passed tests 2763
Skipped tests: 299
Affected tests: 0

$\textcolor{green}{\textsf{All tests passed in REPLAYING mode.}}$
View the build log

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

Terraform GA: Diff ( 4 files changed, 8 insertions(+), 14 deletions(-))
Terraform Beta: Diff ( 4 files changed, 8 insertions(+), 14 deletions(-))

[modular-magician]

Tests analytics

Total tests: 3065
Passed tests 2766
Skipped tests: 299
Affected tests: 0

$\textcolor{green}{\textsf{All tests passed in REPLAYING mode.}}$
View the build log

[c2thorn]

LGTM, can you change the changelog?