docs(ngBindHtml): fix awkward wording

changes: 
 * @ngdoc directive
 * @name ngBindHtml
 *
 * @description
 * Creates a binding that will innerHTML the result of evaluating the `expression` into the current
 * element in a secure way.  By default, the innerHTML-ed content will be sanitized using the {@link
 * ngSanitize.$sanitize $sanitize} service.  To utilize this functionality, ensure that `$sanitize`
 * is available, for example, by including {@link ngSanitize} in your module's dependencies (not in
 * core Angular). In order to use {@link ngSanitize} in your module's dependencies, you need to
 * include "angular-sanitize.js" in your application.

to this:
/**
 * @ngdoc directive
 * @name ngBindHtml
 *
 * @description
 * The ngBindHtml attribute tells Angular to replace the inner HTML content of the specified HTML 
 * element with the value of a given expression, and to update the inner HTML content when the value 
 * of that expression changes in a secure way.  By default, the innerHTML-ed content will be sanitized 
 * using the {@link ngSanitize.$sanitize $sanitize} service.  To utilize this functionality, ensure 
 * that `$sanitize` is available, for example, by including {@link ngSanitize} in your module's 
 * dependencies (not in core Angular). In order to use {@link ngSanitize} in your module's dependencies, 
 * you need to include "angular-sanitize.js" in your application.