Update caption of 'SafeBrowsingForTrustedSourcesEnabled' policy.

Change the caption to follow the policy caption pattern.

Change-Id: I0746c5a9b83ac2f0483cac6c23ff5682cff35128
Reviewed-on: https://chromium-review.googlesource.com/1033418Reviewed-by: Marc-André Decoste <mad@chromium.org>
Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Commit-Queue: Owen Min <zmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#554788}

components/policy/resources/policy_templates.json

@@ -2180,7 +2180,7 @@
       },
       'example_value': False,
       'id': 375,
-      'caption': '''Safe Browsing enable state for trusted sources''',
+      'caption': '''Enable Safe Browsing for trusted sources''',
       'tags': ['local-data-access'],
       'desc': '''Identify if <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph> can allow download without Safe Browsing checks when it's from a trusted source.