kea: depend on the concrete log4cplus, not the -any virtual

kea: depend on the concrete log4cplus, not the -any virtual

Commit 1ea43c352 ("kea: fix kea-libs dependencies") replaced the
direct +log4cplus dependency on kea-libs with the virtual name
+log4cplus-any. With only one log4cplus implementation in the feed,
nothing actually PROVIDES log4cplus-any other than the auto-generated
"package name + -any" alias on log4cplus itself.

apk treats `-any`-suffixed names as ambiguous virtuals that the
admin must resolve explicitly, even when only one provider exists,
and refuses to install:

  ERROR: unable to select packages:
    log4cplus-any (virtual):
      note: please select one of the 'provided by'
            packages explicitly
      provided by: log4cplus
      required by: kea-libs-3.0.2-r7[log4cplus-any]

That bubbles up to every kea subpackage runtime test in CI
(kea-admin, kea-ctrl, every kea-dhcp* and kea-hook-*) and fails
the multi-arch test build with exit code 3.

Switch back to +log4cplus directly; the +libstdcpp addition from
that earlier commit stays — it was the genuinely useful part of
the change. Bump PKG_RELEASE for the redo.

Signed-off-by: Alexandru Ardelean <redacted>