Bump dtolnay/rust-toolchain

Bumps [dtolnay/rust-toolchain](https://github.com/dtolnay/rust-toolchain) from d8352f6b1d2e870bc5716e7a6d9b65c4cc244a1a to 21dc36fb71dd22e3317045c0c31a3f4249868b17.
- [Release notes](https://github.com/dtolnay/rust-toolchain/releases)
- [Commits](dtolnay/rust-toolchain@d8352f6...21dc36f)

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

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

.github/workflows/checks.yml

@@ -44,7 +44,7 @@ jobs:
         run: echo "TARGET_RUST_VERSION=$(if [ "${{matrix.rust}}" = "msrv" ]; then grep rust-version Cargo.toml | grep MSRV | cut -d'"' -f2; else echo "${{matrix.rust}}"; fi)" >> $GITHUB_ENV
 
       - name: Install toolchain
-        uses: dtolnay/rust-toolchain@d8352f6b1d2e870bc5716e7a6d9b65c4cc244a1a
+        uses: dtolnay/rust-toolchain@21dc36fb71dd22e3317045c0c31a3f4249868b17
         with:
           toolchain: "${TARGET_RUST_VERSION}"
           targets: "${{ matrix.target }}"
@@ -88,7 +88,7 @@ jobs:
           persist-credentials: false
 
       - name: Install nightly toolchain
-        uses: dtolnay/rust-toolchain@d8352f6b1d2e870bc5716e7a6d9b65c4cc244a1a
+        uses: dtolnay/rust-toolchain@21dc36fb71dd22e3317045c0c31a3f4249868b17
         with:
           toolchain: nightly
 
@@ -109,7 +109,7 @@ jobs:
           persist-credentials: false
 
       - name: Install rust toolchain
-        uses: dtolnay/rust-toolchain@d8352f6b1d2e870bc5716e7a6d9b65c4cc244a1a
+        uses: dtolnay/rust-toolchain@21dc36fb71dd22e3317045c0c31a3f4249868b17
         with:
           toolchain: stable
           components: rustfmt
@@ -141,7 +141,7 @@ jobs:
           persist-credentials: false
 
       - name: Install rust toolchain
-        uses: dtolnay/rust-toolchain@d8352f6b1d2e870bc5716e7a6d9b65c4cc244a1a
+        uses: dtolnay/rust-toolchain@21dc36fb71dd22e3317045c0c31a3f4249868b17
         with:
           toolchain: stable
           components: clippy