fix: Use stable rust

Author: thebongy

.github/workflows/build.yml

@@ -47,6 +47,7 @@ jobs:
       - name: Install Rust toolchain
         uses: actions-rs/toolchain@v1
         with:
+          toolchain: stable
           profile: minimal
           override: true
 
@@ -88,6 +89,7 @@ jobs:
       - name: Install Rust toolchain
         uses: actions-rs/toolchain@v1
         with:
+          toolchain: stable
           profile: minimal
           override: true