Update thread_pool.h

include/spdlog/details/thread_pool.h

@@ -50,7 +50,6 @@ struct async_msg : log_msg_buffer
     {}
 
     async_msg &operator=(async_msg &&other)
-
     {
         *static_cast<log_msg_buffer *>(this) = std::move(other);
         msg_type = other.msg_type;
@@ -118,4 +117,4 @@ private:
 
 #ifdef SPDLOG_HEADER_ONLY
 #include "thread_pool-inl.h"
-#endif
\ No newline at end of file
+#endif