Upgrade plan button should work for both SaaS and self-managed accounts

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Problem to solve

When viewing the View Jira issues in Gitlab feature, in the Jira integration with a lower tier plan than required, we display an "Upgrade plan" button. This button currently only works for gitlab.com users, not for self-managed instances.

Users on self-managed plans with lower tier plans see a blank area instead of the "Upgrade plan" button.

Self-managed (current)	Self-managed (expected)

For more context, see: #229584 (comment 392457802)