Actions: Fix missing Rust toolchain

Author: qoh

.github/workflows/ci.yml

@@ -11,6 +11,7 @@ jobs:
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal
+          toolchain: stable
           override: true
       - uses: actions-rs/cargo@v1
         with:
@@ -24,6 +25,7 @@ jobs:
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal
+          toolchain: stable
           override: true
       - uses: actions-rs/cargo@v1
         with:
@@ -37,6 +39,7 @@ jobs:
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal
+          toolchain: stable
           override: true
           components: rustfmt
       - uses: actions-rs/cargo@v1
@@ -52,6 +55,7 @@ jobs:
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal
+          toolchain: stable
           override: true
           components: clippy
       - uses: actions-rs/cargo@v1