Set upper limit for the Goda & Atkinson cross-correlation coeffient

[raoanirudh]

The original formulation does not explicitly support PGA, so the engine implementation treats PGA as equivalent to SA(0.05). But this can lead to correlation coefficients > 1.0 for IMT pairs like {PGA, SA(0.1)}. Here, we simply limit the correlation coefficient to have an upper bound of 1.0.

[raoanirudh]

As a side note, #7741 added a method to compute the cross-correlation matrix in the abstract base class, so perhaps the same method implemented for the GodaAtkinson2009 class can be safely replaced by the one in the base class @micheles ?

[micheles]

Maybe, you can try that and see if any tests breaks. For what concerns this PR, all looks good to me and I am going to merge it, after you update the changelog.