regress/rpki-client: test openssl in regress target only

[Klemens Nanni]

Spotted in `make obj' from /usr/src:

        ===> regress/usr.sbin/rpki-client/libressl
        /usr/src/regress/usr.sbin/rpki-client/libressl/obj -> 
/usr/obj/regress/usr.sbin/rpki-client/libressl
        Run "pkg_add openssl--%1.1" to run tests against OpenSSL 1.1
        SKIPPED
        ===> regress/usr.sbin/snmpd

OK?

Index: Makefile
===================================================================
RCS file: /cvs/src/regress/usr.sbin/rpki-client/Makefile,v
retrieving revision 1.10
diff -u -p -r1.10 Makefile
--- Makefile    9 Nov 2020 15:49:48 -0000       1.10
+++ Makefile    7 Nov 2021 22:11:52 -0000
@@ -4,7 +4,7 @@ SUBDIR += libressl
 .if exists(/usr/local/bin/eopenssl11)
 SUBDIR += openssl11
 .else
-.END:
+regress:
        @echo 'Run "pkg_add openssl--%1.1" to run tests against OpenSSL 1.1'
        @echo SKIPPED
 .endif