Replace Riot with Element in docs and comments

This only covers the simple cases of references to issues and repos. More
complex areas, such as deployment scripts, will be handled separately.

Part of https://github.com/vector-im/element-web/issues/14864

src/editor/caret.ts

@@ -59,7 +59,7 @@ export function setCaretPosition(editor: HTMLDivElement, model: EditorModel, car
             // If the selection matches, it's important to leave it alone.
             // Recreating the selection state in at least Chrome can cause
             // strange side effects, like touch bar flickering on every key.
-            // See https://github.com/vector-im/riot-web/issues/9299
+            // See https://github.com/vector-im/element-web/issues/9299
             return;
         }
     }

src/editor/deserialize.ts

@@ -158,7 +158,7 @@ function checkDescendInto(node) {
 
 function checkIgnored(n) {
     if (n.nodeType === Node.TEXT_NODE) {
-        // riot adds \n text nodes in a lot of places,
+        // Element adds \n text nodes in a lot of places,
         // which should be ignored
         return n.nodeValue === "\n";
     } else if (n.nodeType === Node.ELEMENT_NODE) {