The api `Set labels for an issue` may has bug

ref: [xrkffgg/test-ci] Month Statistics: 2020-12 · Issue #55 · xrkffgg/test-ci · GitHub

Set labels for an issue
Removes any previous labels and sets the new labels for an issue.

There are 2 steps to remove and add. In this two-step operation, there should be some problems, resulting in some confusion in the order of adding and removing.