Update cfgov-sheer-templates version

[virginiacc]

Update cfgov-sheer-templates to pull in new mega menu header styles

Changes

• Bump cfgov-sheer-templates to v2.1.6

Testing

• Check out branch
• Run frontendbuild.sh
• Navigate to OAH page other than home page and verify that Consumer Tools section of menu is styled like screenshot

Screenshots

Checklist

• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows the standards laid out in the front end playbook
• Passes all existing automated tests
• New functions include new tests
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged
• Visually tested in supported browsers and devices
• Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)