Several builds ago Microsoft changed the sharing dialog for the Windows 10 Creators Update which finally replaced the older sidebar menu that slid out from the right hand side of the desktop. That UI originated back in Windows 8 and was initially implemented in Microsoft's touch first UI approach.
It stuck around as the focus shifted from touch to using Windows 8.1 and Windows 10 with a mouse and keyboard. Now the company is changing it for a much better dialog that pops up on the middle of your desktop when you click the sharing icon throughout the Creators Update for Windows 10.
However, the new dialog box, like other areas of Windows 10, is a target for app suggestions and in the latest builds of the Creators Update Microsoft has that switched on by default.
Here is what you might see when sharing something in the current build:
As you can see, Microsoft is suggesting that the Line app might be of interest to you as a possible sharing target.
Right now there is no option in the Windows Settings app to turn this feature off however, if you right click on any of the listed apps in the sharing dialog you will see a context menu that allows you to turn off the suggested apps.
Of course, this is still pre-release software so this might disappear before the Creators Update reaches general availability but since suggested apps are a theme in other areas of the OS I expect this to stick around.