Add sharing hub v1.5 to testing config

Bug: None
Change-Id: I308907a247ab9c7ba99f354eedab7672e4fb8a68
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2527681Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Gayane Petrosyan <gayane@chromium.org>
Cr-Commit-Position: refs/heads/master@{#825855}

testing/variations/fieldtrial_testing_config.json

@@ -1533,7 +1533,8 @@
                     "enable_features": [
                         "ChromeShareQRCode",
                         "ChromeShareScreenshot",
-                        "ChromeSharingHub"
+                        "ChromeSharingHub",
+                        "ChromeSharingHubV15"
                     ],
                     "min_os_version": "5.1"
                 }