Implement text color changes across components

The commit involves modifications in various components to change 'text-gray-500' to 'text-muted-foreground'. The purpose of this change is to create uniformity in text colors across the application, enhancing the user interface's overall look and making color scheme tweaks easier in the future.

packages/billing/gateway/src/components/billing-session-status.tsx

@@ -69,9 +69,7 @@ function SuccessSessionStatus({
           🎉
         </Heading>
 
-        <div
-          className={'flex flex-col space-y-4 text-gray-500 dark:text-gray-400'}
-        >
+        <div className={'text-muted-foreground flex flex-col space-y-4'}>
           <p>
             <Trans
               i18nKey={'billing:checkoutSuccessDescription'}

packages/billing/gateway/src/components/pricing-table.tsx

@@ -12,7 +12,6 @@ import { Badge } from '@kit/ui/badge';
 import { Button } from '@kit/ui/button';
 import { Heading } from '@kit/ui/heading';
 import { If } from '@kit/ui/if';
-import { Separator } from '@kit/ui/separator';
 import { Trans } from '@kit/ui/trans';
 import { cn } from '@kit/ui/utils';