[bfcache] Update fieldtrial testing config for `BFCachePerformanceManagerPolicy`

We have decided[1] to continue with cachesize=6. The config needs update
to support further ramping up the traffic in Finch.

[1]: https://crbug.com/1395281#c28

Bug: 1395281
Change-Id: I8273eb7a8fa383d71a3f615c099c3d9260d6857e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4560452
Reviewed-by: Rakina Zata Amni <rakina@chromium.org>
Commit-Queue: Rakina Zata Amni <rakina@chromium.org>
Auto-Submit: Ming-Ying Chung <mych@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1148829}
diff --git a/testing/variations/fieldtrial_testing_config.json b/testing/variations/fieldtrial_testing_config.json
index cab4192..5ad8f212 100644
--- a/testing/variations/fieldtrial_testing_config.json
+++ b/testing/variations/fieldtrial_testing_config.json
@@ -1735,9 +1735,9 @@
             ],
             "experiments": [
                 {
-                    "name": "EnabledPolicy_CacheSize3_20230328",
+                    "name": "EnabledPolicy_CacheSize6_20230525",
                     "params": {
-                        "cache_size": "3",
+                        "cache_size": "6",
                         "foreground_cache_size": "0"
                     },
                     "enable_features": [