WB-1635.fix - Fix border issue on Button.secondary (#2124)

## Summary:

In #2112, I introduced a new `labelStyle` prop and refactored the styles for the
secondary button. However, I missed a case where the border was not being
applied correctly, causing the button from being cut off in certain scenarios.
This PR fixes that issue by including the `border` in the resting/default state,
so the button is always rendered with a border (including that as part of
the box model).

NOTE: The issue was noticed while trying to integrate the changes in webapp.

<img width="621" alt="Screenshot 2023-11-15 at 6 00 42 PM" src="https://github.com/Khan/wonder-blocks/assets/843075/32f76420-1aff-47c9-ad34-cb4aa8976bff">

Issue: WB-1635

## Test plan:

Verify that the secondary button is rendered correctly in all scenarios. This
means that now secondary buttons will always have a border in the resting state.

Author: jandrade

Reviewers: jeresig

Required Reviewers:

Approved By: jeresig

Checks: ✅ codecov/project, ✅ Chromatic - Get results on regular PRs (ubuntu-latest, 16.x), ✅ Test (ubuntu-latest, 16.x, 2/2), ✅ Lint (ubuntu-latest, 16.x), ✅ Check build sizes (ubuntu-latest, 16.x), ✅ Test (ubuntu-latest, 16.x, 1/2), ✅ Chromatic - Build on regular PRs / chromatic (ubuntu-latest, 16.x), ⏭  Chromatic - Skip on Release PR (changesets), ✅ Publish npm snapshot (ubuntu-latest, 16.x), ✅ Check for .changeset entries for all changed files (ubuntu-latest, 16.x), ✅ gerald, ✅ Prime node_modules cache for primary configuration (ubuntu-latest, 16.x), ⏭  dependabot

Pull Request URL: #2124

.changeset/red-maps-talk.md

@@ -0,0 +1,5 @@
+---
+"@khanacademy/wonder-blocks-button": patch
+---
+
+Fix border issue with secondary kind