fix: use semantic card border color for cards

[jhoward-eightfold]

SUMMARY:

This update corrects the card component to use the semantically named card-border-color instead of the generic border-color

GITHUB ISSUE (Open Source Contributors)

#701

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 down PR code
• run storybook
• in the card story, turn off dropshadow and turn on bordered
• ensure card has a border color
• inspect the element and confirm it is now using a semantic css vawriable

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