alex: drop obsolete versions 2.3.1, 2.3.2, 2.3.3, 3.0.1, 3.0.2, and 3.0.5
haddock: drop obsolete versions 2.4.2, 2.7.2, 2.9.2, 2.9.4, 2.11.0, 2.12.0, 2.13.2, 2.13.2.1, 2.14.2, and 2.14.3