tests/test-backwards-remove.t

repoview: flag `server.view` as experimental

Ideally, the non-experimental version of `experimental.extra-filter-revs` will
cover the use case for `server.view=immutable` well enough than having to have
this dedicated configuration. Since `server.view` is not part of any release, I
would prefer to have it marked as experimental to avoid having it to support it
for ever.

  $ hg init
  $ echo This is file a1 > a
  $ hg add a
  $ hg commit -m "commit #0"
  $ ls
  a
  $ echo This is file b1 > b
  $ hg add b
  $ hg commit -m "commit #1"
  $ hg co 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

B should disappear

  $ ls
  a