Fix bug for <legend> in Visualforce specific styles

[thvd]

Changes proposed in this PR:

• Fix bug for <legend> in Visualforce styles. The legend is bold in Visualforce, but it shouldn't be:

Preview:

[salesforce-ux-bot]

By analyzing the blame information on this pull request, we identified @aputinski, @stefsullrew and @kaelig to be potential reviewers

[kaelig]

Thanks for your contribution, @thvd. We really appreciate your help. I'll let @stefsullrew and @brandonferrua review your contribution.

We do require a signed CLA for any contribution, so before we can merge your pull request you'll need to complete the following steps:
https://github.com/salesforce-ux/design-system/blob/master/CONTRIBUTING.md

The good news is that you only have to do this once. Thanks for contributing, and we look forward to integrating your improvements.

[brandonferrua]

Looks good! Thanks for the contribution!

[thvd]

@kaelig I've signed the Contributor License Agreement.

[kaelig]

Thank you again for your contribution, @thvd! The fix is part of today's v2.0.3 release 🎉