Water de/adsorption associated with single‐crystal‐to‐single‐crystal structural transformation of a series of two‐dimensional metal–organic frameworks, [M(bipy)(C 4 O 4 )(H 2 O) 2 ]·3H 2 O (M = Mn (1), Fe (2), and Zn (3), and bipy=4,4′‐bipyridine)