#3027422 Buttons: More sentence-casing for button labels

Changes proposed in this Pull Request

• Fixing a few stray uses of Title Case button labels to use Sentence casing

Testing instructions

• Checkout this branch locally or use https://calypso.live/?branch=update/more-button-sentence-casing
• Visit the pages listed below to check the buttons have proper casing.

My Home

Domains > { registered domain } > Contacts and Privacy

Domains > { registered domain } > Contacts and Privacy > Edit contact info

Domains > { registered domain } > Transfer Domain > Transfer to another registrar

Domains > { registered domain } > Transfer Domain > Transfer to another user

Domains (with empty cart) > Cart button in section header

People > Invites > Invite Details

Settings > Delete your site permanently

Settings > Delete your site permanently > click Delete site

Fixes #40120