Remove remaining crypto references

Closes https://github.com/neovim/docs/pull/26

Also added stubs for 'cryptmethod' and 'key', and placeholders for
explanation regarding removal of crypto functionality.
Merge pull request #1563 from Pyrohh/cleanup-docs-encryption

doc: remove remaining crypto references
Allow most old tests to pass with nocp.

test69.in:
    because 'nocp' sets 'esckeys', add an extra <esc> to avoid 'tm' pause.
Allow the rest of the old tests to pass with nocp.

test40.in, test60.in, test_breakindent.in, test_listlbr.in, test_listlbr_utf8.in:
    To avoid <tab> triggering wildmode, set wildchar to 'cp' default.

test_breakindent.ok:
    Modify expectations to avoid cpoptions+=n