Fix: modify sub nav divider and center aligned

[jjjaspher]

Please always provide the GitHub issue(s) your PR is for, as well as test URLs where your change can be observed (before and after):

Fix https://github.com/hlxsites/accenture-newsroom/issues/483

• https://github.com/hlxsites/accenture-newsroom/issues/483

Test URLs:

• Before: https://main--accenture-newsroom--hlxsites.hlx.page/
• After: https://sub-nav-divider--accenture-newsroom--hlxsites.hlx.page/

[aem-code-sync[bot]]

Hello, I'm the AEM Code Sync Bot and I will run some test suites that validate the page speed. In case there are problems, just click the checkbox below to rerun the respective action.

• [ ] Re-run PSI Checks

[aem-code-sync[bot]]

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