Update CCA version number to 6.0.0

This CL updates version number to 6.0.0. On a second thought, I think
jumping the number to major release level is more clear.

Bug: 935051
Test: None
Change-Id: I735c7214c395da1043ff188ff7072c9880e22b19
Reviewed-on: https://chromium-review.googlesource.com/c/1485622Reviewed-by: Ricky Liang <jcliang@chromium.org>
Commit-Queue: Sheng-hao Tsao <shenghao@google.com>
Cr-Commit-Position: refs/heads/master@{#635412}

chrome/browser/resources/chromeos/camera/src/manifest.json

@@ -3,7 +3,7 @@
   "manifest_version": 2,
   "name": "__MSG_name__",
   "description": "__MSG_description__",
-  "version": "5.4.0",
+  "version": "6.0.0",
   "default_locale": "en",
   "minimum_chrome_version": "60.0.0.0",
   "icons": {