ci: build: use ubuntu-20.04

Signed-off-by: Jianhui Zhao <zhaojh329@gmail.com>

.github/workflows/build.yml

@@ -2,7 +2,7 @@ name: build
 on: push
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - run: sudo apt install -y libev-dev libssl-dev
       - uses: actions/checkout@v2

README_ZH.md

@@ -10,7 +10,7 @@
 [8]: https://github.com/zhaojh329/rtty/releases
 [9]: https://github.com/zhaojh329/rtty/workflows/build/badge.svg
 [10]: https://img.shields.io/badge/支持rtty-赞助作者-blueviolet.svg
-[11]: https://gitee.com/zhaojh329/rtty#贡献代码
+[11]: #贡献代码
 [12]: https://img.shields.io/badge/技术交流群-点击加入：153530783-brightgreen.svg
 [13]: https://jq.qq.com/?_wv=1027&k=5PKxbTV