Remove the --speech-service-key command line flag.

It is not used anymore. The standard API keys workflow should be
used instead.
See http://www.chromium.org/developers/how-tos/api-keys.

BUG=350333

Review URL: https://codereview.chromium.org/189603005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255749 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255749