fix(docs): SegementedButton theme docs (#4031)

Co-authored-by: Ben Steel <ben@think-now.com>
Co-authored-by: Luke Walczak <lukasz.walczak.pwr@gmail.com>

Author: 3 people

docs/src/data/themeColors.js

@@ -302,7 +302,6 @@ const themeColors = {
     },
     unchecked: {
       '-': {
-        backgroundColor: 'theme.colors.primary + 12% transparency',
         textColor: 'theme.colors.onSurface',
         borderColor: 'theme.colors.outline',
       },