JIT: revise comment about struct-of-struct-of-field promotion (#22952)
JIT: revise comment about struct-of-struct-of-field promotion (#22952)

Fixes an oversight in #22867.
poizan42/coreclr,cshung/coreclr,cshung/coreclr,cshung/coreclr,cshung/coreclr,krk/coreclr,mmitche/coreclr,poizan42/coreclr,krk/coreclr,wtgodbe/coreclr,krk/coreclr,mmitche/coreclr,mmitche/coreclr,mmitche/coreclr,mmitche/coreclr,poizan42/coreclr,wtgodbe/coreclr,wtgodbe/coreclr,poizan42/coreclr,krk/coreclr,wtgodbe/coreclr,wtgodbe/coreclr,wtgodbe/coreclr,krk/coreclr,cshung/coreclr,cshung/coreclr,poizan42/coreclr,krk/coreclr,poizan42/coreclr,mmitche/coreclr