The file name of the .desktop file for the OpenJDK policytool contains the full package version string:

java-1.8.0-openjdk-1.8.0.111-3.b16.fc26.x86_64-policytool.desktop

This means that there is no good way of hiding this entry from the gnome-shell applications list. Hiding entries is usually done by creating a modified copy of that file in ~/.local/share/applications/ with the same file name as the original and changing the "NoDisplay" value. But since the file name changes with every update of the openjdk package, this would have to repeated every time the package is updated.

Also the version string is exposed in the user visible "Name" entry of that file and for some reason it even made it into the "Comment" entry.