docs/devel/migration.rst: spelling fixes: doen't, diferent, responsability, recomend

Fixes: 593c28c02c81 "migration/doc: How to migrate when hosts have different features"
Fixes: 1aefe2ca1423 "migration/doc: Add documentation for backwards compatiblity"
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
1 file changed