Remove obsolete property from plugin.properties
Remove obsolete property from plugin.properties

Review URL: http://codereview.chromium.org/146028
AlexRee/chromedevtools,AlexRee/chromedevtools,vpupkin/chromedevtools,AlexRee/chromedevtools,ericmckean/chromedevtools,AlexRee/chromedevtools,ericmckean/chromedevtools,vpupkin/chromedevtools,ericmckean/chromedevtools,ericmckean/chromedevtools,vpupkin/chromedevtools,vpupkin/chromedevtools,ericmckean/chromedevtools,vpupkin/chromedevtools,AlexRee/chromedevtools