Read Me First section: Remove statement of support for Internet Explo…

…rer (pull #1305)

Modifies the browser subsection of read me first front matter to remove IE from list of browsers where testing is done.
First step in resolution of issue #1304.

Co-authored-by: Matt King <a11yThinker@Gmail.com>

aria-practices.html

@@ -140,8 +140,8 @@ <h3>Browser and Assistive Technology Support</h3>
         It is thus advisable to test implementations thoroughly with each browser and assistive technology combination that is relevant within a target audience.
       </p>
       <p>
-        Similarly, JavaScript and CSS in this guide is written to be compatible with the most recent version of Chrome, Firefox, Internet Explorer, and Safari at the time of writing.
-        In particular, some JavaScript and CSS may not function correctly in Internet Explorer version 10 or earlier.
+        Similarly, JavaScript and CSS in this guide is written to be compatible with the most recent version of Chrome, Firefox, and Safari at the time of writing.
+Some JavaScript and CSS may not function correctly in Internet Explorer.
       </p>
       <p>
         Except in cases where the ARIA Working Group and other contributors have overlooked an error,