[Encrypted files, symlink] Move encrypted file and symlink target

Since I am moving away from $HOME/.emacs.d, the last remaining file in
this directory has been moved to the equivalent $HOME/.config/emacs.

The $HOME/.emacs.d symlink also now points to a relative path, making it
username-agnostic.

.config/yadm/encrypt

@@ -1,4 +1,4 @@
 .authinfo.gpg
 .ssh/*
-.emacs.d/private/private_emacs.el
+.config/emacs/private/private_emacs.el
 .mailrc

.emacs.d

@@ -1 +1 @@
-/home/phundrak/.config/emacs
+.config/emacs/