packaging/debian: drop librdkafka version dependency [upstreamonly]

The reason we are dropping the >= dependency in our Build-Depends is
that older Debian/Ubuntu versions that we still want to build for
may have an old version of librdkafka and we want the build-deps to
be satisfied even in this case.

When this happens the configure script will refuse to use the installed
librdkafka version and build syslog-ng _without_ rdkafka support,
which is exactly what we want.

If the librdkafka version is good enough, we would build librdkafka
as well (e.g. debian sid for instance).

Signed-off-by: Balazs Scheidler <bazsi77@gmail.com>

packaging/debian/control

@@ -34,7 +34,7 @@ Build-Depends: debhelper (>= 10~),
                libcurl4-openssl-dev,
                libsnappy-dev,
                libsnmp-dev [linux-any hurd-i386],
-               librdkafka-dev (>= 1.0.0),
+               librdkafka-dev,
                openjdk-8-jdk <!nojava>
 Build-Conflicts: autoconf2.13
 Standards-Version: 4.4.1