Fix Free Art License v1.3 link (flameshot-org#2311)

The README had a dead link.

(cherry picked from commit 62d4643)

README.md

@@ -474,7 +474,7 @@ Note: If you install from source, there is no uninstaller, you will need to manu
 
 ## License
 - The main code is licensed under [GPLv3](LICENSE)
-- The logo of Flameshot is licensed under [Free Art License v1.3](img/app/flameshotLogoLicense.txt)
+- The logo of Flameshot is licensed under [Free Art License v1.3](data/img/app/flameshotLogoLicense.txt)
 - The button icons are licensed under Apache License 2.0. See: /~https://github.com/google/material-design-icons
 - The code at capture/capturewidget.cpp is based on /~https://github.com/ckaiser/Lightscreen/blob/master/dialogs/areadialog.cpp (GPLv2)
 - The code at capture/capturewidget.h is based on /~https://github.com/ckaiser/Lightscreen/blob/master/dialogs/areadialog.h (GPLv2)