Remove the LICENSE file install from upstream as debian already installs it.
--- a/meson.build
+++ b/meson.build
@@ -487,11 +487,9 @@
 ]
 
 install_man(man_files)
-install_data(['AUTHORS', 'LICENSE.md', 'LICENSE_sleef.txt'],
+install_data(['AUTHORS'],
              rename : [
 	       'doc/siril/AUTHORS',
-	       'doc/siril/LICENSE.md',
-	       'doc/siril/LICENSE_sleef.txt',
 	     ],
              install_dir : siril_share)
 
