Use correct interface name in preferences_manifest.json.

Use correct interface name in preferences_manifest.json.

Should be prefs::mojom::PreferencesServiceFactory, instead of
prefs::mojom::PreferencesFactory.

Otherwise there would have bellowing ERROR log:
[99556:99581:0217/140056.829661:ERROR:service_manager.cc(209)]
Connection InterfaceProviderSpec prevented service: content_browser from
binding interface: prefs::mojom::PreferencesServiceFactory exposed by:
preferences

BUG=

[leonhsl(Using Gerrit), 2017-02-17 07:02:18]

The CQ bit was checked by leon.han@intel.com to run a CQ dry run

[commit-bot: I haz the power, 2017-02-17 07:02:42]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[leonhsl(Using Gerrit), 2017-02-17 07:05:04]

leon.han@intel.com changed reviewers:
+ jonross@chromium.org, sky@chromium.org

[leonhsl(Using Gerrit), 2017-02-17 07:05:05]

PTAL, Thanks.

[commit-bot: I haz the power, 2017-02-17 08:19:46]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-02-17 08:19:48]

Dry run: Try jobs failed on following builders:
  android_n5x_swarming_rel on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/android_n5x_...)

[leonhsl(Using Gerrit), 2017-02-17 08:23:18]

The CQ bit was checked by leon.han@intel.com to run a CQ dry run

[commit-bot: I haz the power, 2017-02-17 08:23:52]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-02-17 08:56:40]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-02-17 08:56:41]

Dry run: This issue passed the CQ dry run.

[jonross, 2017-02-17 10:52:05]

On 2017/02/17 07:05:05, leonhsl wrote:
> PTAL, Thanks.

Thanks for spotting this. We currently have this covered in a patch that
addresses a few other errors with preferences as well:
https://codereview.chromium.org/2698913005/ so we can just land that instead.