fix: 调整uts-syntaxcase iOS 避免云打包报错

uni_modules/uts-syntaxcase/utssdk/index.uts

@@ -128,6 +128,6 @@ class RequestTaskImpl implements RequestTask {
     }
 }
 
-export function request(url : string) : RequestTask {
+export function request(url : string) : RequestTask | null {
     return new RequestTaskImpl(url)
 }
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