Don't prevent tabbing to `Run SQL` button (#117)

See comment in #115

datasette/templates/database.html

@@ -93,7 +93,8 @@
     editor.setOption("extraKeys", {
       "Shift-Enter": function() {
         document.getElementsByClassName("sql")[0].submit();
-      }
+      },
+      Tab: false
     });
 </script>