Bump cachix/cachix-action from 14 to 15 in the actions-deps group

Bumps the actions-deps group with 1 update: [cachix/cachix-action](https://github.com/cachix/cachix-action).


Updates `cachix/cachix-action` from 14 to 15
- [Release notes](https://github.com/cachix/cachix-action/releases)
- [Commits](cachix/cachix-action@v14...v15)

---
updated-dependencies:
- dependency-name: cachix/cachix-action
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: actions-deps
...

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

Author: dependabot[bot]

.github/workflows/check-ios-android-bindings.yml

@@ -30,7 +30,7 @@ jobs:
           # Mostly to avoid GitHub rate limiting
           extra_nix_config: |
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
-      - uses: cachix/cachix-action@v14
+      - uses: cachix/cachix-action@v15
         with:
           name: xmtp
           authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
@@ -63,7 +63,7 @@ jobs:
           # Mostly to avoid GitHub rate limiting
           extra_nix_config: |
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
-      - uses: cachix/cachix-action@v14
+      - uses: cachix/cachix-action@v15
         with:
           name: xmtp
           authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'