disable robotjs-based tests

See #18409

spec/api-menu-spec.js

@@ -835,7 +835,9 @@ describe('Menu module', () => {
     })
   })
 
-  describe('menu accelerators', () => {
+  // FIXME(nornagon): this is disabled due to an issue with nan in current v8.
+  // See https://github.com/electron/electron/issues/18409
+  describe.skip('menu accelerators', () => {
     let testFn = it
     try {
       // We have other tests that check if native modules work, if we fail to require

spec/api-web-contents-spec.js

@@ -382,7 +382,9 @@ describe('webContents module', () => {
     })
   })
 
-  describe('devtools window', () => {
+  // FIXME(nornagon): this is disabled due to an issue with nan in current v8.
+  // See https://github.com/electron/electron/issues/18409
+  describe.skip('devtools window', () => {
     let testFn = it
     if (process.platform === 'darwin' && isCi) {
       testFn = it.skip