scepclient: Remove documentation about removal of scepclient

There should be no need for such a persistent documentation on a removed
component in the repository.  The commit history is enough.  And besides
that, there is user-facing documentation about it in the docs and the
changelog/NEWS.

src/scepclient/README.md

@@ -1,18 +0,0 @@
-# ipsec scepclient #
-
-## Description ##
-
-The `ipsec scepclient` tool was an early client implementation of the
-_Simple Certificate Enrollment Protocol_ (SCEP).
-
-The tool was written in 2005 and only got marginal updates since then. Hence it
-implemented an old version of the SCEP Internet Draft (version 10/11 of
-`draft-nourse-scep` and used the broken `MD5` hash and single `DES` encryption
-algorithms as defaults.
-
-## Obsolescence ##
-
-With strongSwan version 5.9.8 `*ipsec scepclient*` has been removed and replaced
-by the `pki` subcommands `pki --scep` and `pki --scepca` which implement the new
-SCEP RFC 8894 standard that was released in September 2020 and which supports
-trusted **certificate renewal** based on the existing client certificate.