By Ayeesha Walsh Prince Harry and Meghan Markle appeared all smiles as they headed to a charity polo match for the final leg of their Nigerian tour. The couple were guests of honour at the fundraising event held in aid of “support and uplift of injured veterans.” Meghan, 42, optedfor her third outfit change of the day and appeared to be in good spirits as she joined Harry to watch the tournament. Dressed in a summery beige halterneck maxi-dress Meghan beamed with delight as they posed for pictures upon arriving at the event. Earlier in the day Meghan had opted for two more colourful outfits do…