Change behold to beware (#3494)

Author: nekename

_includes/app_notes.html

@@ -6,7 +6,7 @@ <h2 id="installation">Usage</h2>
 Most AppImages run on recent versions of Arch Linux, CentOS, Debian, Fedora, openSUSE, Red Hat, Ubuntu, and other common desktop distributions.</p>
 <h3>Running {{ page.name | remove: ".md" }} on Linux without installation</h3>
 Unlike other applications, AppImages do not need to be installed before they can be used. However, they need to be marked as executable before they can be run. This is a Linux security feature.</p>
-<p><b>Behold!</b> AppImages are usually not verified by others. Follow these instructions only if you trust the developer of the software. Use at your own risk!</p>
+<p><b>Beware!</b> AppImages are usually not verified by others. Follow these instructions only if you trust the developer of the software. Use at your own risk!</p>
 <p>Download the {{ page.name | remove: ".md" }} AppImage and <a href="https://discourse.appimage.org/t/how-to-run-an-appimage/80">make it executable using your file manager</a> or by entering the following commands in a terminal:</p>
 <div class="highlight">
   <span class="mega-octicon octicon-terminal"></span>