Remove inline onclick handler for Open DevTools button in index.html as it is already in the renderer process

Author: vorlie

index.html

@@ -106,7 +106,7 @@ <h2 class="modal-h2">About</h2>
                         <p id="chromeVersion" class="version">Chrome Version: </p>
                     </div>
                     <button class="about-button" onclick="checkForUpdates()">Check for Updates</button>
-                    <button class="about-button" id="open-dev-tools" onclick="window.API.openDevTools()">Open DevTools</button>
+                    <button class="about-button" id="open-dev-tools">Open DevTools</button>
                     <button class="about-button" id="open-theme-editor">Open Theme Editor</button>
                 </div>
             </div>