a11y: Added focus border on Tabs.

[rmotwani-c-eightfold]

SUMMARY:

• Added focus border on Tabs.

GITHUB ISSUE (Open Source Contributors)

JIRA TASK (Eightfold Employees Only):

Jira task - https://eightfoldai.atlassian.net/browse/ENG-117818

CHANGE TYPE:

• Bugfix Pull Request
• Feature Pull Request

TEST COVERAGE:

• Tests for this change already exist
• I have added unittests for this change

TEST PLAN:

• pull branch down locally and start storybook (yarn storybook)
• Navigate to the tabs component, and using tab focus on any of the tabs and observe that a focus border is visible.

UI Impact:

• Go to - /position/pipeline_v2?pid=481052551587&review_mode=pipeline_v2_leads
• Switch to - demo@starbucks-dev-sandbox.com
• Inside Right panel, navigate to the tabs sections and check that the focus border is visible on the tabs.

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[ykelkar-eightfold]

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