Update dtolnay/rust-toolchain digest to 686976e (#10433)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
|
[dtolnay/rust-toolchain](https://redirect.github.com/dtolnay/rust-toolchain)
([changelog](https://redirect.github.com/dtolnay/rust-toolchain/compare/6bed0761d98439e5a578e2877258200ad565ba87..686976e191b89faba57d3206551f0f330d8cb249))
| action | digest | `6bed076` → `686976e` |

---

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.github/actions/setup-prebuild/action.yml

@@ -48,7 +48,7 @@ runs:
 
     - name: Install Rust
       if: github.repository == 'vortex-data/vortex' && steps.check-rustup.outputs.exists != 'true'
-      uses: dtolnay/rust-toolchain@6bed0761d98439e5a578e2877258200ad565ba87  # stable
+      uses: dtolnay/rust-toolchain@686976e191b89faba57d3206551f0f330d8cb249  # stable
       with:
         toolchain: ${{ steps.toolchain-config.outputs.toolchain }}
         targets: ${{ inputs.targets }}

.github/actions/setup-rust/action.yml

@@ -46,7 +46,7 @@ runs:
 
     - name: Rust Toolchain
       id: rust-toolchain
-      uses: dtolnay/rust-toolchain@6bed0761d98439e5a578e2877258200ad565ba87  # stable
+      uses: dtolnay/rust-toolchain@686976e191b89faba57d3206551f0f330d8cb249  # stable
       if: steps.check-rustup.outputs.exists != 'true'
       with:
         toolchain: "${{ steps.toolchain-config.outputs.toolchain }}"