use alt-g for filter bufferlist

this is more consistent with the other existing shortcuts and is also
the same shortcut go.py recommends in weechat-curses

index.html

@@ -113,7 +113,7 @@
                   <li>ALT-[0-9]: Focus on buffer</li>
                   <li>ALT-a: Focus on next buffer with activity</li>
                   <li>ALT-<: Switch to previous buffer</li>
-                  <li>CTRL+G: Focus on buffer list filter</li>
+                  <li>ALT+G: Focus on buffer list filter</li>
                   <li>escape: disconnect</li>
                   <li>arrow keys: history navigation</li>
                 </ul>

js/glowingbear.js

@@ -1056,8 +1056,8 @@ weechat.directive('inputBar', function() {
                     return true;
                 }
 
-                // Ctrl+G -> focus on buffer filter input
-                if ($event.ctrlKey && (code === 103 || code === 71)) {
+                // Alt+G -> focus on buffer filter input
+                if ($event.altKey && (code === 103 || code === 71)) {
                     $event.preventDefault();
                     document.getElementById('bufferFilter').focus();
                     return true;