You have received a standard email notifying you of a schedule amendment. But as brunos says, for a 30 minute schedule change (which also gives you a shorter journey) you won't be entitled to a free change. The schedule amendment would need to be over 2 hours as another poster highlighted above to qualify for a free involuntary change. You are also not entitled to a free change due to a change of aircraft type (unless you were flying business and had lost a qsuite assignment)

So please be careful. Switching to the morning flight would be a voluntary change in this circumstance, and is likely to cost you not only the fare difference for the whole ticket (outbound and return if there is a return portion unused), but also any change fee due according to the fare rules of your original ticket. Cancelling may also incur a penalty.