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/components/views/room_settings/AliasSettings.js

@@ -233,7 +233,7 @@ export default class AliasSettings extends React.Component {
     onLocalAliasDeleted = (index) => {
         const alias = this.state.localAliases[index];
         // TODO: In future, we should probably be making sure that the alias actually belongs
-        // to this room. See https://github.com/vector-im/riot-web/issues/7353
+        // to this room. See https://github.com/vector-im/element-web/issues/7353
         MatrixClientPeg.get().deleteAlias(alias).then(() => {
             const localAliases = this.state.localAliases.filter(a => a !== alias);
             this.setState({localAliases});

src/components/views/room_settings/ColorSettings.js

@@ -39,7 +39,7 @@ const ROOM_COLORS = [
 
 // Dev note: this component is not attached anywhere, but is left here as it
 // has a high possibility of being used in the nearish future.
-// Ref: https://github.com/vector-im/riot-web/issues/8421
+// Ref: https://github.com/vector-im/element-web/issues/8421
 
 export default createReactClass({
     displayName: 'ColorSettings',