Is it possible to use just one shared folder for log shipping? I wonder if it is possible to use one shared folder(only in source database) instead of two (one in source db and another in destination db). That's Server1 will store its t-log backups there and Server2 will restore those backups from the same folder. Please see images below to understand what I mean:
Yes you can, I remember a shop where we had this kind of setup in that case even the copy job was disabled because there were no need to copy the files. 
You just need to be sure your file retention is ok and the Share is available at all the times. You don't want your share folder go offline during a long weekend or something and your transaction log on prod gets full.