Follow the directions below to hide any AU plug-ins (UAD or otherwise) from Logic Pro X:

Logic Pro X features a “Plug-in Manager” window that allows you to hide individual plug-ins from plug-in lists within Logic. To access the Plug-in Manager window, choose “Preferences > Plug-in Manager…” from under the “Logic Pro X” menu at upper left of the display. Uncheck the “Use” box next to an individual plug-in to hide that plug-in from the lists within Logic Pro X.