[stable/2023.1] Bump MCAPI to 0.18.0 (#1271)

This is an automated cherry-pick of #1258
/assign mnaser

images/magnum/Dockerfile

@@ -21,7 +21,7 @@ RUN --mount=type=cache,mode=0755,target=/root/.cache/pip,sharing=private <<EOF b
 pip3 install \
     --constraint /upper-constraints.txt \
         /src/magnum \
-        magnum-cluster-api==0.16.0
+        magnum-cluster-api==0.18.0
 EOF
 
 FROM registry.atmosphere.dev/library/openstack-python-runtime:${RELEASE}