Fixed copyright message in AOMContentAXTree by removing the (C) symbol

Chromium's new copyright message doesn't have a (C) symbol.
Files created in the last few years should be using the new copyright message.,

Change-Id: I653ea93d569c8eb21810007dad9df1021d9cf532
Reviewed-by: Nektarios Paisios <>
Reviewed-by: Dominic Mazzoni <>
Commit-Queue: Nektarios Paisios <>
Commit-Queue: Dominic Mazzoni <>
Cr-Commit-Position: refs/heads/master@{#631306}
2 files changed