select the pink color with the "eyedropper" color selector. change it to the background color by clicking the "foreground/background" color boxes. Use the eraser tool to wipe away the black letters. Or use the cloning tool, select an area in the pink background, then wipe away the letters with the cloning tool ( hold down the left mouse or trackpad button and drag the cloning tool over the area you want to remove )
Work on a copy of your file in case something goes wrong.