ci: update dtolnay/rust-toolchain requirement to 29eef336d9b2848a0b548edc03f92a220660cdb8 (#87)

Updates the requirements on [dtolnay/rust-toolchain](https://github.com/dtolnay/rust-toolchain) to permit the latest version.
- [Release notes](https://github.com/dtolnay/rust-toolchain/releases)
- [Commits](https://github.com/dtolnay/rust-toolchain/commits/29eef336d9b2848a0b548edc03f92a220660cdb8)

---
updated-dependencies:
- dependency-name: dtolnay/rust-toolchain
  dependency-version: 29eef336d9b2848a0b548edc03f92a220660cdb8
  dependency-type: direct:production
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -64,7 +64,7 @@ jobs:
             rust: "1.85"  # MSRV
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # actions/checkout v6
-      - uses: dtolnay/rust-toolchain@3c5f7ea28cd621ae0bf5283f0e981fb97b8a7af9 # dtolnay/rust-toolchain master
+      - uses: dtolnay/rust-toolchain@29eef336d9b2848a0b548edc03f92a220660cdb8 # dtolnay/rust-toolchain master
         with:
           toolchain: ${{ matrix.rust }}
       - uses: Swatinem/rust-cache@e18b497796c12c097a38f9edb9d0641fb99eee32 # Swatinem/rust-cache v2