feat(unity-bootstrap-theme): improve accessibility by increasing text contrast (WCAG AAA compliance)

Increase text contrast to meet WCAG AAA (changed #747474 → #484848)

UDS-2040

Author: juanmitriatti

packages/unity-bootstrap-theme/src/scss/extends/_video.scss

@@ -8,7 +8,7 @@
       align-items: center;
 
       figcaption {
-        color: $uds-color-base-gray-5;
+        color: $uds-color-base-gray-6;
         font-size: $uds-size-font-tiny;
         margin: $uds-size-spacing-1 $uds-size-spacing-2 $uds-size-spacing-2
           $uds-size-spacing-2;