Delete unused file expandarray.h (#15204)
Delete unused file expandarray.h (#15204)

This was used by the JIT but now it has its own copy (src\jit\jitexpandarray.h).
mmitche/coreclr,wtgodbe/coreclr,krk/coreclr,wtgodbe/coreclr,JosephTremoulet/coreclr,yizhang82/coreclr,ruben-ayrapetyan/coreclr,wtgodbe/coreclr,JosephTremoulet/coreclr,krk/coreclr,wtgodbe/coreclr,krk/coreclr,mmitche/coreclr,JosephTremoulet/coreclr,JosephTremoulet/coreclr,yizhang82/coreclr,cshung/coreclr,ruben-ayrapetyan/coreclr,mmitche/coreclr,cshung/coreclr,cshung/coreclr,poizan42/coreclr,poizan42/coreclr,yizhang82/coreclr,poizan42/coreclr,cshung/coreclr,wtgodbe/coreclr,yizhang82/coreclr,krk/coreclr,poizan42/coreclr,mmitche/coreclr,cshung/coreclr,cshung/coreclr,mmitche/coreclr,wtgodbe/coreclr,JosephTremoulet/coreclr,ruben-ayrapetyan/coreclr,ruben-ayrapetyan/coreclr,yizhang82/coreclr,poizan42/coreclr,mmitche/coreclr,krk/coreclr,ruben-ayrapetyan/coreclr,poizan42/coreclr,krk/coreclr,ruben-ayrapetyan/coreclr,yizhang82/coreclr,JosephTremoulet/coreclr