feat：getSymbolSt支持usdc

@@ -330,7 +330,8 @@ class CmBroker
     public function getSymbolSt($symbol)
     {
         $symbol = str_replace('-USDT-SWAP', 'USDT',  $symbol);
-        if (preg_match('/^[A-Z0-9]+USDT$/', $symbol)) {
+        $symbol = str_replace('-USDC-SWAP', 'USDC',  $symbol);
+        if (preg_match('/^[A-Z0-9]+USD[CT]$/', $symbol)) {
             if ($this->plat == self::PLAT_BINANCE || $this->plat == self::PLAT_BYBIT) {
                 $num = SymbolInfo::extractNumber($symbol);
                 $symbol = str_replace($num, '', $symbol);