Fix manage typo in named port description

[magul]

It fixes a typo in description of google_compute_instance_group_named_port

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• [ ] Generated Terraform, and ran make test and make lint to ensure it passes unit and linter tests.
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[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 1 file changed, 2 insertions(+), 2 deletions(-)) Terraform Beta: Diff ( 1 file changed, 2 insertions(+), 2 deletions(-)) TF Validator: Diff ( 2 files changed, 3 insertions(+), 3 deletions(-))