ci: opt-out of checkout persist credentials.

See actions/checkout#485

Author: cpu

.github/workflows/ci.yml

@@ -10,6 +10,8 @@ jobs:
     runs-on: windows-latest
     steps:
     - uses: actions/checkout@master
+      with:
+        persist-credentials: false
     - name: Install Rust
       uses: dtolnay/rust-toolchain@master
       with:
@@ -40,6 +42,8 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@master
+      with:
+        persist-credentials: false
     - name: Install Rust
       uses: dtolnay/rust-toolchain@master
       with: