MINISERIES PREMIERE: Part 3 of 3. This is the conclusion of J.K. Rowling’s miniseries, which stars Michael Gambon as the prominent patriarch of a small British town, trying to steer a public election to favor the transformation of a rehabilitative halfway house to a luxury hotel and spa. There are a few good performances, but this final episode takes an unforgivably bleak turn, and also, on balance, isn’t that good, period. If it were, would HBO be showing this miniseries on a Wednes