Fix remaining strict types errors

[millnut]

With Drupal core moving towards strict types, more info we should fix the remaining errors suppressed in the phpstan baseline.

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  Line   modules/contrib/localgov_workflows/modules/localgov_workflows_notifications/src/Form/LocalgovServiceContactForm.php
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  74     Method Drupal\localgov_workflows_notifications\Form\LocalgovServiceContactForm::validateForm() should return Drupal\Core\Entity\ContentEntityInterface but return statement is missing.
  81     Method Drupal\localgov_workflows_notifications\Form\LocalgovServiceContactForm::validateForm() should return Drupal\Core\Entity\ContentEntityInterface but return statement is missing.
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  Line   modules/contrib/localgov_workflows/modules/localgov_workflows_notifications/src/WorkflowNotification.php
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  62     Variable $queue_item might not be defined.
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