pom.xml: updates for release 0.124
pom.xml: updates for release 0.124

Update killbill-client -> 0.36
Update killbill-api -> 0.43

Signed-off-by: Kill Bill core team <1a73af9e7ae00182733b2292511b814be66f065f@killbill.io>

killbill/killbill-oss-parent