password_manager::features::kEnablePasswordChangeSupport is no longer used since r414350, we should remove it completely.

Also, in components/autofill/content/renderer/form_autofill_util.cc,  IsFormVisible still contains code excluded from OS_ANDROID. This code can potentially lead to Chrome understanding more submission events as success (by returning false). The code was not used on Android when Android did not have the "Update password?" prompt, to protect users from rewriting a good credential by some misunderstood other content. Now that Android has the update prompt, there is no need for running different checks on Android, and we should remove the non-Android #ifdefs.