cmd/gomobile: remove outdated TODO of bundle ID

The TODO message was introduced in CL 13041, but later resolved
in CL 77070 because it allows bundle id customization.

Remove the oudated TODO message.

Change-Id: Ib32793ace937f67b5c95d6efadd6d4eef48a8986
Reviewed-on: https://go-review.googlesource.com/c/mobile/+/369200
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Trust: Alex Rakoczy <alex@golang.org>
Run-TryBot: Alex Rakoczy <alex@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

Author: changkun

cmd/gomobile/build_apple.go

@@ -33,7 +33,6 @@ func goAppleBuild(pkg *packages.Package, bundleID string, targets []targetInfo)
 
 	infoplist := new(bytes.Buffer)
 	if err := infoplistTmpl.Execute(infoplist, infoplistTmplData{
-		// TODO: better bundle id.
 		BundleID: bundleID + "." + productName,
 		Name:     strings.Title(path.Base(pkg.PkgPath)),
 	}); err != nil {