Null-check call result rather than function itself

From the comment, it seems like this was supposed check for chords, rather than checking for the availability of `isChord`.

Signed-off-by: Andrew Casey <andrew.casey@microsoft.com>

packages/monaco/src/browser/monaco-resolved-keybinding.ts

@@ -49,7 +49,7 @@ export class MonacoResolvedKeybinding extends monaco.keybindings.ResolvedKeybind
     }
 
     public getElectronAccelerator(): string | null {
-        if (this.isChord) {
+        if (this.isChord()) {
             // Electron cannot handle chords
             // eslint-disable-next-line no-null/no-null
             return null;