Incrementing VERSION to 73.0.3683.4

TBR=govind@chromium.org

Change-Id: Id9a3f237122ff52b85a76758edf9d1f41ba89d58
Reviewed-on: https://chromium-review.googlesource.com/c/1437835
Reviewed-by: chrome-release-bot@chromium.org <chrome-release-bot@chromium.org>
Cr-Commit-Position: refs/branch-heads/3683@{#7}
Cr-Branched-From: e510299-refs/heads/master@{#625896}

chrome/VERSION

@@ -1,4 +1,4 @@
 MAJOR=73
 MINOR=0
 BUILD=3683
-PATCH=3
+PATCH=4