[BUG] HeaderNavControl missing border at right

[Hailong-am]

Describe the bug

When register more than one navControl on header, the border is missing between them.

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior

Border should displayed

OpenSearch Version
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Dashboards Version
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Plugins

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Screenshots

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Host/Environment (please complete the following information):

• OS: [e.g. iOS]
• Browser and version [e.g. 22]

Additional context

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[AMoo-Miki]

@kgcreative can you please comment on this?

[kgcreative]

Yes please -- there needs to be an option for having multiple dividers between items.