### Purpose
This is a [new function](https://pkg.go.dev/slices@go1.21.0#Contains)
added in the go1.21 standard library, which can make the code more
concise and easy to read.
### Testing
Describe what testing has been done, and how the reviewer can test the
change
if new tests are not included.
### Screenshots
If this is a GUI change, include screenshots of the change. If not,
please
feel free to just delete this section.
### Documentation
If this is a user visible change (including API and protocol changes),
add a link here
to the corresponding pull request on https://github.com/syncthing/docs
or describe
the documentation changes necessary.
## Authorship
Your name and email will be added automatically to the AUTHORS file
based on the commit metadata.
Signed-off-by: dashangcun <907225865@qq.com>
Co-authored-by: Jakob Borg <jakob@kastelo.net>
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