Allow metric changes for 9.2.8 as baseline is from a release pipeline

Metric Decrease:
    haddock.base
    haddock.Cabal
    haddock.compiler
Metric Increase:
    ManyAlternatives
    ManyConstructors
    T10421
    T10858
    T12227
    T12425
    T12707
    T13035
    T13253
    T13719
    T15164
    T16577
    T18304
    T18698a
    T18698b
    T3294
    T5321FD
    T5642
    T9203
    T9233
    T9630
    T9872a
    T9872b
    T9872c
    T9872d
    T14697
    T12545
    T1969
    parsing001