[Designer] Fix contrast ratios for button borders

[RebeccaAnne]

Related Issue

Fixes ADO 30642435 and 30926378

Description

Darken the border of buttons in order to meet accessibility contrast ratio requirements. Contrast ratio between background and button border is now 3.366:1

How Verified

Confirmed contrast ratio of buttons in the designer using accessibility insights.

Microsoft Reviewers: Open in CodeFlow

[ghost]

Hi @RebeccaAnne. Thanks for helping make the AdaptiveCards JS renderer + tooling better. As additional verification, once the JS build succeeds, please go to the test site to test out your website/designer changes.

[ghost]

Hi @RebeccaAnne. This non-spec pull request has had no recent activity for the past 5 days . Please take the necessary actions (review, address feedback or commit if reviewed already) to move this along.

[ghost]

Hi @RebeccaAnne; Thanks for taking action on your previously stale pull request. Resetting staleness.

[almedina-ms]

/azp run AdaptiveCards-iOS-CI

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[ghost]

Hi @RebeccaAnne. This non-spec pull request has had no recent activity for the past 5 days . Please take the necessary actions (review, address feedback or commit if reviewed already) to move this along.

[ghost]

Hi @RebeccaAnne; Thanks for taking action on your previously stale pull request. Resetting staleness.

[ghost]

Hi @RebeccaAnne. This non-spec pull request has had no recent activity for the past 5 days . Please take the necessary actions (review, address feedback or commit if reviewed already) to move this along.

[ghost]

Staleness reset by paulcam206

[ghost]

Hi @RebeccaAnne. This non-spec pull request has had no recent activity for the past 5 days . Please take the necessary actions (review, address feedback or commit if reviewed already) to move this along.

[ghost]

Staleness reset by almedina-ms