treewide: remove FSF address

Remove the paragraph about writing to the Free Software Foundation's
mailing address. The FSF has changed addresses in the past, and may do
so again. In 2021 this is not useful, let's rather have a bit less
boilerplate at the start of source files.

Change-Id: Ic8c69d24141abd183e3b1257f4e9edfd9c1afabe
3 files changed