build-unit-test-docker: eslint-plugin-json: pin to v3.1.0

The new v4.0.0 release does not work with an error like this:
```
Error: ESLint configuration in --config ยป plugin:json/recommended-with-comments is invalid:
	- Unexpected top-level property "files".
```
Pin eslint-plugin-json to v3.1.0 to solve this.

Change-Id: I773c9c0bda3b87cca92e69089ea37fb20f563ab9
Signed-off-by: Xinnan Xie <xiexinnan@bytedance.com>
1 file changed