Update unit tests for va-button and va-button-pair

[rmessina1010]

Description

Relates to:
#2379
Create/updated unit test on va-button and va-button-pair to account for the new submit behavior,

Tasks

• Create unit tests in va-button and va-button-pair

Acceptance Criteria

• Unit tests in va-button and va-button-pair reflect: form.onsubmit(), form.submit(), and button.onclick()

[caw310]

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