Fix dnssecConfig filed on google_dns_managed_zone resource

[Samir-Cit]

This PR fixes the issue hashicorp/terraform-provider-google#17682 by adding a default_from_api: true config on dnssecConfig field on the resouce google_dns_managed_zone.
This will prevent the terraform diff when running a second apply which the resource was changed outside terraform.

Release Note Template for Downstream PRs (will be copied)

dns: fixed permadiff on `dnssec_config` field of `google_dns_managed_zone` resource

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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.

google provider: Diff ( 1 file changed, 1 insertion(+))
google-beta provider: Diff ( 1 file changed, 1 insertion(+))

[modular-magician]

Tests analytics

Total tests: 47
Passed tests: 46
Skipped tests: 1
Affected tests: 0

Click here to see the affected service packages

• dns

$\textcolor{green}{\textsf{All tests passed!}}$

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