ci: Use rust-toolchain file

Author: alixinne

.github/workflows/build.yml

@@ -35,10 +35,8 @@ jobs:
       - name: Install Rust toolchain
         uses: actions-rs/toolchain@v1
         with:
-          toolchain: stable
           target: ${{ matrix.target }}
           profile: minimal
-          override: true
 
       - name: Build Docker image for cross
         working-directory: docker

.github/workflows/docs.yml

@@ -26,9 +26,7 @@ jobs:
       - name: Install Rust toolchain
         uses: actions-rs/toolchain@v1
         with:
-          toolchain: stable
           profile: minimal
-          override: true
 
       - name: Build docs
         uses: actions-rs/cargo@v1