ci: unfreeze wasm-unknown-unknown from rustc 1.81 (#7471)

Signed-off-by: ADD-SP <[email protected]>
Co-authored-by: Taiki Endo <[email protected]>

Author: ADD-SP

.github/workflows/ci.yml

@@ -1038,10 +1038,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - name: Install Rust 1.81
+      - name: Install Rust ${{ env.rust_stable }}
         uses: dtolnay/rust-toolchain@stable
         with:
-          toolchain: 1.81
+          toolchain: ${{ env.rust_stable }}
       - name: Install wasm-pack
         uses: taiki-e/install-action@wasm-pack