core: ignore welcome in ci

packages/hydrooj/src/welcome.ts

@@ -84,6 +84,7 @@ int main() {
 `;
 
 export default async function apply() {
+    if (process.env.CI) return;
     await DomainModel.edit('system', { bulletin });
     const docId = await ProblemModel.add('system', 'P1000', 'A+B Problem', defaultProblem, 1, ['系统测试']);
     // This might fail so we are doing it asynchronously.