Fix typo in VideoCaptureAllowedUrls policy

In the policy description of VideoCaptureAllowedUrls, it says "audio
capture devices...". Instead it should say "video capture devices..".
It was probably caused by copy-pasting.

Bug: 841003
Change-Id: I027e1d5ecaae27263668ef0e97d96434e9418f02
Reviewed-on: https://chromium-review.googlesource.com/1152450Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Commit-Queue: Jialiu Lin <jialiul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578697}

components/policy/resources/policy_templates.json

@@ -6925,7 +6925,7 @@
       'caption': '''URLs that will be granted access to video capture devices without prompt''',
       'tags': ['website-sharing'],
       'desc': '''Patterns in this list will be matched against the security
-      origin of the requesting URL.  If a match is found, access to audio
+      origin of the requesting URL.  If a match is found, access to video
       capture devices will be granted without prompt.
 
       NOTE: Until version 45, this policy was only supported in Kiosk mode.''',