Yes. The old and new libraries refer to the same "phycal" files actually on the hard drive and unless you remove all references to the files (i.e. both of the libraries), you will lose no data. So you may go ahead and remove the old iPhoto library. When migrating to Photos, little or no data at all was actually duplicated, so keep in mind that you will not gain the full 113.2 GB back because those files will still be in the Photos library.