Incrementing VERSION to 71.0.3578.4

TBR=mmoss@chromium.org

Change-Id: Iea1c8832f88e0db26686faff8b2dbeecc3ba9e98
Reviewed-on: https://chromium-review.googlesource.com/c/1279365
Reviewed-by: chrome-release-bot@chromium.org <chrome-release-bot@chromium.org>
Cr-Commit-Position: refs/branch-heads/3578@{#7}
Cr-Branched-From: 4226ddf-refs/heads/master@{#599034}

chrome/VERSION

@@ -1,4 +1,4 @@
 MAJOR=71
 MINOR=0
 BUILD=3578
-PATCH=3
+PATCH=4