Fix unused variables.

Author: mbutrovich

spark/src/main/scala/org/apache/comet/serde/QueryPlanSerde.scala

@@ -2317,7 +2317,7 @@ object QueryPlanSerde extends Logging with CometExprShim {
         None
       }
     } catch {
-      case e: Exception =>
+      case _: Exception =>
         None
     }
   }

spark/src/main/scala/org/apache/spark/sql/comet/CometIcebergNativeScanExec.scala

@@ -291,7 +291,7 @@ object CometIcebergNativeScanExec {
               namespace = namespaceParts,
               tableName = tableNamePart))
         } catch {
-          case e: Exception =>
+          case _: Exception =>
             // If reflection fails, fall back to returning None
             return None
         }