Remove request-assign-future.txt

The preferred way to share request-assign-future.txt is by pointing
to https://orgmode.org/request-assign-future.txt.

To access the text file from a repository, you can find it in the
orgweb repository: https://git.sr.ht/~bzg/orgweb/

README

@@ -28,11 +28,6 @@ instructions at https://orgmode.org/org.html#Installation.
 
 - testing/ :: Testing suite for Org.
 
-- request-assign-future.txt :: The form that contributors have to sign
-  and get processed with the FSF before contributed changes can be
-  integrated into the Org core.  All files in this distribution have
-  copyright assigned to the FSF.
-
 * Join the GNU Project
 
 Org is part of GNU Emacs and GNU Emacs is part of the GNU Operating

mk/targets.mk

@@ -1,7 +1,7 @@
 .EXPORT_ALL_VARIABLES:
 .NOTPARALLEL: .PHONY
 # Additional distribution files
-DISTFILES_extra=  Makefile request-assign-future.txt etc
+DISTFILES_extra=  Makefile etc
 
 LISPDIRS      = lisp
 OTHERDIRS     = doc etc