DevTools: Remove orphaned CSS rules [D]

Source/devtools/front_end/elementsPanel.css:694 select-settings
https://codereview.chromium.org/136613004

Source/devtools/front_end/heapProfiler.css:136 heap-snapshot-help
https://chromiumcodereview.appspot.com/22961005

Source/devtools/front_end/helpScreen.css:444 add-button
https://chromiumcodereview.appspot.com/16689005

Source/devtools/front_end/helpScreen.css:714 help-field-note
https://codereview.chromium.org/372293002

Source/devtools/front_end/helpScreen.css:440 remove-button
https://chromiumcodereview.appspot.com/23784004

Source/devtools/front_end/helpScreen.css:448 workspace-settings-error
https://chromiumcodereview.appspot.com/23784004

Source/devtools/front_end/helpScreen.css:444 workspace-settings-row
https://chromiumcodereview.appspot.com/23784004

BUG=
NOTRY=true

Review URL: https://codereview.chromium.org/415403007

git-svn-id: svn://svn.chromium.org/blink/trunk@179497 bbb929c8-8fbe-4397-9dbb-9b2b20218538