Fix integration test runner

Author: flip1995

.github/workflows/clippy_bors.yml

@@ -222,10 +222,11 @@ jobs:
 
     # Run
     - name: Test ${{ matrix.integration }}
-      run: $CARGO_TARGET_DIR/debug/integration
+      run: |
+        RUSTUP_TOOLCHAIN="$(rustup show active-toolchain | grep -o -E "nightly-[0-9]{4}-[0-9]{2}-[0-9]{2}")" \
+          $CARGO_TARGET_DIR/debug/integration
       env:
         INTEGRATION: ${{ matrix.integration }}
-        RUSTUP_TOOLCHAIN: master
 
   # These jobs doesn't actually test anything, but they're only used to tell
   # bors the build completed, as there is no practical way to detect when a