Apply clang-format

Eigen/src/ThreadPool/ThreadEnvironment.h

@@ -27,7 +27,7 @@ struct StlThreadEnvironment {
     EnvThread(std::function<void()> f) : thr_(std::move(f)) {}
     ~EnvThread() { thr_.join(); }
     // This function is called when the threadpool is cancelled.
-    void OnCancel() { }
+    void OnCancel() {}
 
    private:
     std::thread thr_;