Formatting fix in template.

The headers get swapped by clang-format

Change-Id: I8a95d5789413d6e18ad4bfd545e1a2021eae3d72
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/77444
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

src/sem/intrinsic_type.h.tmpl

@@ -11,8 +11,8 @@ See:
 #ifndef SRC_SEM_INTRINSIC_TYPE_H_
 #define SRC_SEM_INTRINSIC_TYPE_H_
 
-#include <string>
 #include <sstream>
+#include <string>
 
 namespace tint {
 namespace sem {