Update rebate banner to 50% Trading Fee Rebates (#1299)

Author: fionn223

config/localization/en/app.json

@@ -2685,7 +2685,7 @@
     "REBATE_BANNER": {
       "REBATE_BANNER_TITLE": "This September: Get 50% of Trading Fees Back",
       "REBATE_BANNER_TITLE_SURGE": "dYdX Surge:",
-      "REBATE_BANNER_TITLE_FEES": "$1M Rewards Pool + 100% Fee Rebates Live Now",
+      "REBATE_BANNER_TITLE_FEES": "50% Trading Fee Rebates Live Now",
       "REBATE_BANNER_SUBTITLE": "Front-end only",
       "REBATE_BANNER_CTA": "Get Rebate"
     },