chore(rewards): update participant_pending banner copy

Co-authored-by: VGR-GIT <vangulckrik@gmail.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: VGR-GIT

locales/languages/en.json

@@ -8293,8 +8293,8 @@
         "a11y": "Open winner details"
       },
       "participant_pending": {
-        "title": "Determining winners",
-        "description": "We're still determining the winners."
+        "title": "Contest has ended.",
+        "description": "We're determining the contest winners. Check back soon."
       },
       "participant_finalized": {
         "title": "Contest results are in",