Remove `BTab` from `GlTab`
## [BootstrapVue props we should support](https://bootstrap-vue.org/docs/components/tabs#comp-ref-b-tab-props)
- `disabled`
- `id`
- `lazy`
- `title`
- `title-item-class`
- `title-link-attributes`
- `title-link-class`
## [BootstrapVue props we should consider _not_ supporting](https://bootstrap-vue.org/docs/components/tabs#comp-ref-b-tab-props)
https://gitlab-org.gitlab.io/frontend/bootstrapvue-component-usage-breakdown/components.json can be used as a starting point to see if the prop is used, but should not be considered an exhaustive list (it does not check https://gitlab.com/gitlab-org/customers-gitlab-com/ or Switchboard, please do this manually). We should weigh the pros and cons of supporting each prop individually.
- `active`
- `button-id`
- `no-body`
- `tag`
## [BootstrapVue slots we should support](https://bootstrap-vue.org/docs/components/tabs#comp-ref-b-tab-slots)
- `default`
- `title`
## [BootstrapVue events we should support](https://bootstrap-vue.org/docs/components/tabs#comp-ref-b-tab-events)
- `click`
issue