remove the older move --force, which never behaved as documented and seems useless

* move: --force was accidentially enabling two unrelated behaviors
  since 6.20180427. The older behavior, which has never been well
  documented and seems almost entirely useless, has been removed.
* copy: --force no longer does anything.

This commit was sponsored by Øyvind Andersen Holm.

doc/bugs/g-a_move_has_force_option_described_twice/comment_2_71eed2cf7fd21634a2b60ef5cd9ccb93._comment

@@ -0,0 +1,32 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 2"""
+ date="2018-05-21T17:04:56Z"
+ content="""
+Actually the --force documentation re location tracking is not a good
+description of the behavior. It only affects --from, and with --force
+it still contacts the remote to check if it has the content. Only
+if that check fails to return a result (ie, the remote can't be contacted),
+does it assume that the remote has the content, rather than the default
+behavior of falling back to looking at the location tracking information.
+
+It's hard to see how that could be useful at all; if it fails in
+communication with the remote, presumably the content transfer will later
+fail as well.
+
+The only actual behavior change would be when the remote cannot be
+contacted, and the location tracking information says it does not contain a
+file. Then `move --force --from remote` will fail, because it tries
+to perform the move and can't contact the remote, while `move --from
+remote` will succeed, because it assumes the location tracking is right.
+
+That does not seem a useful distinction. And that was the behavior all the
+way back to the first commit of this "feature" in 2013.
+
+So, removing that.
+
+----
+
+There may be room for a new option that actually does whatever you were
+hoping --force did. So let's talk about that..
+"""]]