Remove awesome_nested_set override for ActiveStorage

[kennyadsl]

With 73cd0ef we monkey patched awesome_nested_set to introduce the fix done here: collectiveidea/awesome_nested_set#413.

Now that the PR has been merged, and 3.2.1 released, we can safely remove the override but lock the awesome_nested_set dependency to version 3.2.1.

cc @filippoliverani

[parndt]

Version 3.3.1 of awesome_nested_set has been released, so probably the entire override file can be removed now.

[ikraamg]

@kennyadsl This issue looks solved by your PR, I think we can close it.