[makeself] Fix license URL (#12219)

packaging/makeself/makeself-license.txt

@@ -41,4 +41,4 @@
 
   netdata re-distributes a lot of open source software components.
   Check its full license at:
-  https://github.com/netdata/netdata/blob/master/LICENSE.md
+  https://github.com/netdata/netdata/blob/master/LICENSE