Remove the gulp bundle task since it's unused and doesn't really make sense

Not only is there no code depending on it now, the actual task itself doesn't even make sense as-is. Note that it uses the default `DEFINES` configuration *unaltered*, which is neither useful nor correct since the resulting build thus won't make sense without an actual built target set.

gulpfile.js

@@ -677,13 +677,6 @@ gulp.task("cmaps", function (done) {
   done();
 });
 
-gulp.task(
-  "bundle",
-  gulp.series("buildnumber", function () {
-    return createBundle(DEFINES).pipe(gulp.dest(BUILD_DIR));
-  })
-);
-
 function preprocessCSS(source, mode, defines, cleanup) {
   var outName = getTempFile("~preprocess", ".css");
   builder.preprocessCSS(mode, source, outName);