mailmap: Update entries for Nikita.

* .mailmap: change email and name for Nikita.
* Makefile.am, doc/guix.texi, etc/completion/fish/guix.fish,
gnu/packages/accessibility.scm, gnu/packages/admin.scm,
gnu/packages/audio.scm, gnu/packages/autotools.scm, gnu/packages/cdrom.scm,
gnu/packages/check.scm, gnu/packages/cinnamon.scm,
gnu/packages/compression.scm, gnu/packages/crypto.scm,
gnu/packages/databases.scm, gnu/packages/django.scm, gnu/packages/dns.scm,
gnu/packages/elixir.scm, gnu/packages/emacs-xyz.scm, gnu/packages/emacs.scm,
gnu/packages/enlightenment.scm, gnu/packages/erlang.scm,
gnu/packages/fonts.scm, gnu/packages/fontutils.scm, gnu/packages/forth.scm,
gnu/packages/fvwm.scm, gnu/packages/games.scm, gnu/packages/gl.scm,
gnu/packages/gnome.scm, gnu/packages/gnunet.scm, gnu/packages/gnupg.scm,
gnu/packages/gtk.scm, gnu/packages/guile-wm.scm, gnu/packages/guile-xyz.scm,
gnu/packages/haskell-apps.scm, gnu/packages/haskell-check.scm,
gnu/packages/haskell-crypto.scm, gnu/packages/haskell-xyz.scm,
gnu/packages/haskell.scm, gnu/packages/image-viewers.scm,
gnu/packages/image.scm, gnu/packages/irc.scm, gnu/packages/language.scm,
gnu/packages/libcanberra.scm, gnu/packages/linux.scm,
gnu/packages/lisp-xyz.scm, gnu/packages/lisp.scm, gnu/packages/lolcode.scm,
gnu/packages/lxde.scm, gnu/packages/lxqt.scm, gnu/packages/mail.scm,
gnu/packages/markup.scm, gnu/packages/mate.scm, gnu/packages/maths.scm,
gnu/packages/mc.scm, gnu/packages/messaging.scm, gnu/packages/music.scm,
gnu/packages/ncurses.scm, gnu/packages/networking.scm,
gnu/packages/nickle.scm, gnu/packages/openbox.scm, gnu/packages/pdf.scm,
gnu/packages/perl-check.scm, gnu/packages/perl.scm,
gnu/packages/python-compression.scm, gnu/packages/python-crypto.scm,
gnu/packages/python-web.scm, gnu/packages/python-xyz.scm,
gnu/packages/python.scm, gnu/packages/qt.scm, gnu/packages/ruby.scm,
gnu/packages/rust.scm, gnu/packages/scheme.scm,
gnu/packages/serialization.scm, gnu/packages/shells.scm,
gnu/packages/ssh.scm, gnu/packages/suckless.scm, gnu/packages/tbb.scm,
gnu/packages/telephony.scm, gnu/packages/text-editors.scm,
gnu/packages/textutils.scm, gnu/packages/time.scm, gnu/packages/tls.scm,
gnu/packages/tor.scm, gnu/packages/version-control.scm,
gnu/packages/video.scm, gnu/packages/vim.scm, gnu/packages/web.scm,
gnu/packages/wm.scm, gnu/packages/xdisorg.scm, gnu/packages/xfce.scm,
gnu/packages/xml.scm, gnu/packages/xorg.scm, gnu/services/certbot.scm,
gnu/services/desktop.scm, gnu/services/version-control.scm,
gnu/services/web.scm, guix/import/hackage.scm, guix/licenses.scm: Likewise.

Signed-off-by: Efraim Flashner <efraim@flashner.co.il>