Update docs preview URL in presubmit

NoTry: true
Bug: skia:
Change-Id: Id5b374f707ac44770a5142f104202d6509410767
Reviewed-on: https://skia-review.googlesource.com/129505
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
Commit-Queue: Ravi Mistry <rmistry@google.com>
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index f9747fa..8e33390 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -37,7 +37,7 @@
 
 AUTHORS_FILE_NAME = 'AUTHORS'
 
-DOCS_PREVIEW_URL = 'https://skia.org/?cl='
+DOCS_PREVIEW_URL = 'https://preview.skia.org/?cl='
 GOLD_TRYBOT_URL = 'https://gold.skia.org/search?issue='
 
 # Path to CQ bots feature is described in https://bug.skia.org/4364