net-im/ktp-accounts-kcm: Fix plist, use other subst

This comes from area51, the KDE-FreeBSD staging area.

The fix switches a lib-version substitution from KDE4_VERSION to
KDE4_GENERIC_LIB_VERSION. This is already used in other
peripheral-to-KDE-workspace applications like audio/amarok. This
is preliminary work for KDE4 infrastructure changes.

PR: 209316
Submitted by: groot@kde.org (kde)