Mark CoalesceH2ConnectionsWithClientCertificatesForHosts as internal_only

Change-Id: I3f5bd166da9b104128ade1891e427e8953083c83
Bug: 855690
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2314556Reviewed-by: Owen Min <zmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791066}

components/policy/resources/policy_templates.json

@@ -17717,7 +17717,7 @@
         'items': { 'type': 'string' },
       },
       'supported_on': ['chrome.*:70-','android:70-','chrome_os:70-'],
-      'future': True,
+      'internal_only': True,
       'features': {
         'dynamic_refresh': True,
         'per_profile': True,