rustdoc: when resizing the sidebar to nothing, clear size setting

This way, when the sidebar is restored, it comes back at default size.

Author: notriddle

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

@@ -1248,9 +1248,13 @@ href="https://doc.rust-lang.org/${channel}/rustdoc/how-to-read-rustdoc.html\
     const hideSidebar = () => {
         if (isSrcPage) {
             window.rustdocCloseSourceSidebar();
+            updateLocalStorage("src-sidebar-width", null);
+            document.documentElement.style.removeProperty("--src-sidebar-width");
         } else {
             addClass(document.documentElement, "hide-sidebar");
             updateLocalStorage("hide-sidebar", "true");
+            updateLocalStorage("desktop-sidebar-width", null);
+            document.documentElement.style.removeProperty("--desktop-sidebar-width");
         }
     };
     const showSidebar = () => {