Fix an incorrect header guard.

Typo from when the header got created.

Change-Id: I2fa6bbd90444f6367813efff0e26ed0b84670855
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/79812
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/fpdfsdk/pwl/ipwl_fillernotify.h b/fpdfsdk/pwl/ipwl_fillernotify.h
index e968633..5447a60 100644
--- a/fpdfsdk/pwl/ipwl_fillernotify.h
+++ b/fpdfsdk/pwl/ipwl_fillernotify.h
@@ -4,8 +4,8 @@
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
-#ifndef FPDFSDK_PWL_IFWL_FILLERNOTIFY_H_
-#define FPDFSDK_PWL_IFWL_FILLERNOTIFY_H_
+#ifndef FPDFSDK_PWL_IPWL_FILLERNOTIFY_H_
+#define FPDFSDK_PWL_IPWL_FILLERNOTIFY_H_
 
 #include <utility>
 
@@ -42,4 +42,4 @@
       uint32_t nFlag) = 0;
 };
 
-#endif  // FPDFSDK_PWL_IFWL_FILLERNOTIFY_H_
+#endif  // FPDFSDK_PWL_IPWL_FILLERNOTIFY_H_