Remove @author tags (#5601)

Our files are up to a decade old, and have churned so much, that the initial author of the file no longer has much meaning.

Furthermore, this will encourage developers to post to the developer group, rather than emailing Googlers (usually me) directly.

core/dropdowndiv.js

@@ -8,7 +8,6 @@
 /**
  * @fileoverview A div that floats on top of the workspace, for drop-down menus.
  * The drop-down can be kept inside the workspace, animate in/out, etc.
- * @author tmickel@mit.edu (Tim Mickel)
  */
 
 'use strict';