test: fix strict mode failure

Since the value is undefined at the this point, just remove it so that
linters and strict mode don't cause the entire test suite to abort.

test/browser.multiapp.test.js

@@ -55,7 +55,6 @@ describe('browser support for multiple apps', function() {
 
 function browserifyTestApps(apps, next) {
   var b = browserify({
-    basedir: appDir,
     debug: true
   });