build(deps): bump rvolosatovs/nix-flake-update-action

Bumps [rvolosatovs/nix-flake-update-action](https://github.com/rvolosatovs/nix-flake-update-action) from 2.0.5 to 3.0.0.
- [Release notes](https://github.com/rvolosatovs/nix-flake-update-action/releases)
- [Commits](rvolosatovs/nix-flake-update-action@7249aa6...fbf9785)

---
updated-dependencies:
- dependency-name: rvolosatovs/nix-flake-update-action
  dependency-version: 3.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/update.yml

@@ -9,7 +9,7 @@ jobs:
   nix-flake-update:
     runs-on: ubuntu-24.04
     steps:
-      - uses: rvolosatovs/nix-flake-update-action@7249aa67d87e2a195c376fe34c230af0862a9900 # v2.0.5
+      - uses: rvolosatovs/nix-flake-update-action@fbf9785a8c450529ebd91985bcd167089081e52e # v3.0.0
         with:
           app-id: ${{ secrets.BOT_APP_ID }}
           private-key: ${{ secrets.BOT_APP_PRIVATE_KEY }}