Move pragma once in rolling/jit/operation.hpp. (#16636)

I noticed from #16590 (comment) that there was one other file where `#pragma once` was not at the top. This PR fixes that.

Authors:
  - Bradley Dice (https://github.com/bdice)

Approvers:
  - Vyas Ramasubramani (https://github.com/vyasr)

URL: #16636

cpp/src/rolling/jit/operation.hpp

@@ -14,12 +14,12 @@
  * limitations under the License.
  */
 
+#pragma once
+
 #include "rolling/jit/operation-udf.hpp"
 
 #include <cudf/types.hpp>
 
-#pragma once
-
 struct rolling_udf_ptx {
   template <typename OutType, typename InType>
   static OutType operate(InType const* in_col, cudf::size_type start, cudf::size_type count)