Two Files icons in Ubuntu 20.04 application launcher

As you mentioned in the comments the following information on .desktop files on your system:

/usr/share/applications/org.gnome.Nautilus.desktop:Name=Files
/usr/share/applications/nemo.desktop:Name=Files
/usr/share/applications/csd-automount.desktop:Name=Files

it is clear that you also have a different file manager installed, "Nemo", or at least had it installed at one time. Anyway, its desktop file is still there.

One .desktop file is for file manager nautilus, the default file manager on an Ubuntu desktop. The other .desktop file is for nemo, a different file manager used as default in the Cinnamon desktop.

To avoid having two files icons, either

• Remove nemo (never remove your default file manager), which will remove the .desktop file
• If you wish to keep nemo, you can change the name of its icon by editing the .desktop file, so you can easily distinguish the icons.

To change the name of the icon for nemo:

1. Copy the file /usr/share/applications/nemo.desktop to the folder .local/share/applications in your home directory.
2. Edit the copy with your text editor and change Name=Files to, for example, Name=Nemo File Manager.
3. Save the file and close the editor.

The changed copy of the nemo.desktop file will override the system wide one. Accordingly, that icon will now appear as "Nemo File Manager".