Bump actions/cache/restore from 5.0.5 to 6.1.0

Bumps [actions/cache/restore](https://github.com/actions/cache) from 5.0.5 to 6.1.0.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@27d5ce7...55cc834)

---
updated-dependencies:
- dependency-name: actions/cache/restore
  dependency-version: 6.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/csharp_test.yml

@@ -43,7 +43,7 @@ jobs:
     - uses: actions/setup-dotnet@9a946fdbd5fb07b82b2f5a4466058b876ab72bb2 # v5.3.0
       with:
         dotnet-version: 9
-    - uses: actions/cache/restore@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
+    - uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
       with:
         path: |
           ./binding/voicevox_core/target/release/libvoicevox_core.so
@@ -74,7 +74,7 @@ jobs:
     - uses: actions/setup-dotnet@9a946fdbd5fb07b82b2f5a4466058b876ab72bb2 # v5.3.0
       with:
         dotnet-version: 9
-    - uses: actions/cache/restore@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
+    - uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
       with:
         path: |
           ./binding/voicevox_core/target/release/libvoicevox_core.so