[Extensions] Update Page Action Manifest Tests to manifest v2

We should (finally) remove support for manifest v1. One of the last
significant dependencies is that a lot of our tests aren't manifest v2
yet.

This CL updates the majority of manifest files under
chrome/test/data/extensions/page_actions (which are not usually
named manifest.json).

This CL only modifies files that update cleanly (i.e., no other
test updates necessary). A separate CL will address those.

Bug: 816679
Change-Id: I5bbb98be75c9a1912e3221095d8aa4db1ba6f7d2
Reviewed-on: https://chromium-review.googlesource.com/952270Reviewed-by: Istiaque Ahmed <lazyboy@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541484}

chrome/test/data/extensions/page_action/page_action_default_popup.json

 {
    "name": "PageAction Test",
+   "manifest_version": 2,
    "version": "1.0",
    "page_action": {
       "default_icon": "image1.png",

chrome/test/data/extensions/page_action/page_action_empty.json

 {
    "name": "PageAction Test",
+   "manifest_version": 2,
    "version": "1.0",
    "page_action": { }
 }

chrome/test/data/extensions/page_action/page_action_empty_default_popup.json

 {
    "name": "PageAction Test",
+   "manifest_version": 2,
    "version": "1.0",
    "page_action": {
       "default_icon": "image1.png",

chrome/test/data/extensions/page_action/page_action_new_format.json

 {
    "name": "PageAction Test",
+   "manifest_version": 2,
    "version": "1.0",
    "page_action": {
       "default_icon": "image1.png",