main.js: make hideAllModals docs clearer

"true" looks like a string value, `true` makes it more clear
that we are talking about the actual boolean value.

Author: lolbinarycat

src/librustdoc/html/static/js/main.js

@@ -1593,7 +1593,7 @@ function preLoadCss(cssUrl) {
     /**
      * Hide popover menus, clickable tooltips, and the sidebar (if applicable).
      *
-     * Pass "true" to reset focus for tooltip popovers.
+     * Pass `true` to reset focus for tooltip popovers.
      */
     window.hideAllModals = switchFocus => {
         hideSidebar();