Update fieldtrial testing config for TLS 1.3 trial bump.

Change-Id: I9618c48fbdaa277070e67f3f1371eba341df00e8
Reviewed-on: https://chromium-review.googlesource.com/1244556Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: David Benjamin <davidben@chromium.org>
Commit-Queue: Steven Valdez <svaldez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594368}

testing/variations/fieldtrial_testing_config.json

@@ -4291,9 +4291,9 @@
             ],
             "experiments": [
                 {
-                    "name": "Draft23V4",
+                    "name": "FinalV6",
                     "params": {
-                        "variant": "draft23"
+                        "variant": "final"
                     }
                 }
             ]