fix(iOS): fix iOS DRM header parser (#3609)

ios/Video/DataStructures/DRMParams.swift

@@ -25,6 +25,16 @@ struct DRMParams {
         self.contentId = json["contentId"] as? String
         self.certificateUrl = json["certificateUrl"] as? String
         self.base64Certificate = json["base64Certificate"] as? Bool
-        self.headers = json["headers"] as? [String: Any]
+        if let headers = json["headers"] as? [[String: Any]] {
+            var _headers: [String: Any] = [:]
+            for header in headers {
+                if let key = header["key"] as? String, let value = header["value"] {
+                    _headers[key] = value
+                }
+            }
+            self.headers = _headers
+        } else {
+            self.headers = nil
+        }
     }
 }