Bump insta from 1.42.2 to 1.43.1 in /backend

Bumps [insta](https://github.com/mitsuhiko/insta) from 1.42.2 to 1.43.1.
- [Release notes](https://github.com/mitsuhiko/insta/releases)
- [Changelog](https://github.com/mitsuhiko/insta/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mitsuhiko/insta/compare/1.42.2...1.43.1)

---
updated-dependencies:
- dependency-name: insta
  dependency-version: 1.43.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

backend/sync_lib/Cargo.toml

@@ -23,7 +23,7 @@ console_error_panic_hook = { version = "0.1.7", optional = true }
 
 [dev-dependencies]
 wasm-bindgen-test = "0.3.49"
-insta = "1.42.2"
+insta = "1.43.1"
 
 [features]
 default = ["console_error_panic_hook"]