Web Locks API: Remove unnecessary binding reference for renderers

The blink.mojom.LockManager registration is exposed via execution
context parameterized binding (frames, dedicated/share/service
workers); it does not need to be exposed at the service manager
(renderer proces host) level.

Change-Id: Idc033a65a9d5646310434d52756333daba68d23e
Reviewed-on: https://chromium-review.googlesource.com/1181923
Commit-Queue: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584673}

content/public/app/mojo/content_browser_manifest.json

@@ -42,7 +42,6 @@
           "blink.mojom.EmbeddedFrameSinkProvider",
           "blink.mojom.FileUtilitiesHost",
           "blink.mojom.FileSystemManager",
-          "blink.mojom.LockManager",
           "blink.mojom.Hyphenation",
           "blink.mojom.MimeRegistry",
           "blink.mojom.PluginRegistry",