Apply dsf to google_compute_health_check port value with no portspec

[modular-magician]

Fixes #7586

port_specification was a later addition to this API, and if it has no value the resource uses the value in port > port_name. As such, we can apply this DSF in that case as well.

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Release Note Template for Downstream PRs (will be copied)

compute: fixed an issue where `google_compute_health_check` `port` values caused a diff when `port_specification` was unset or set to `""`

Derived from GoogleCloudPlatform/magic-modules#4143

[Chupaka]

Btw that fixes #7210 :)

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