timing: Remove redundant include file

There is no need to include winbase.h, as it will be pulled in by
windows.h as needed.

Fixes #2640
diff --git a/ChangeLog b/ChangeLog
index 985a4b1..a4f83d8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -43,6 +43,7 @@
      codes to always wrap these codes into X.509 high level error codes before
      returning. Fixes #2431.
    * Fix typo in net_would_block(). Fixes #528 reported by github-monoculture.
+   * Remove redundant include file in timing.c. Fixes #2640 reported by irwir.
 
 Changes
    * Return from various debugging routines immediately if the