Revert "Prevent gnc-commodity from marking the book dirty at file-load."

This reverts commit 8be7d15e1df0171dc2551085629b2588790aea10 because it
prevents the book from being marked dirty under most circumstances, not
just when loading commodities.

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23767 57a11ea4-9604-0410-9ed3-97b8803252fd