Bump pyrefly from 1.1.1 to 1.2.0 in /backend

Bumps [pyrefly](https://github.com/facebook/pyrefly) from 1.1.1 to 1.2.0.
- [Release notes](https://github.com/facebook/pyrefly/releases)
- [Commits](facebook/pyrefly@1.1.1...1.2.0)

---
updated-dependencies:
- dependency-name: pyrefly
  dependency-version: 1.2.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

backend/pyproject.toml

@@ -55,7 +55,7 @@ dev = [
     "mypy==2.3.0",
     "pluggy==1.6.0",
     "pylint==4.0.2",
-    "pyrefly==1.1.1",
+    "pyrefly==1.2.0",
     "pytest-asyncio==1.4.0",
     "pytest-cov==7.1.0",
     "pytest-xdist==3.8.0",