ci: pin the rust version for wasm tests (#7518)

(cherry picked from commit 987675e843)

.github/workflows/ci.yml

@@ -991,10 +991,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - name: Install Rust 1.81
+      - name: Install Rust 1.88.0
         uses: dtolnay/rust-toolchain@stable
         with:
-          toolchain: 1.81
+          toolchain: 1.88.0
       - name: Install wasm-pack
         uses: taiki-e/install-action@wasm-pack
 
@@ -1014,10 +1014,10 @@ jobs:
           - wasm32-wasip1-threads
     steps:
       - uses: actions/checkout@v4
-      - name: Install Rust ${{ env.rust_stable }}
+      - name: Install Rust 1.88.0
         uses: dtolnay/rust-toolchain@stable
         with:
-          toolchain: ${{ env.rust_stable }}
+          toolchain: 1.88.0
           targets: ${{ matrix.target }}
 
       # Install dependencies