Bump C++ client to 4.2.0 (#306)

dependencies.yaml

diff --git a/dependencies.yaml b/dependencies.yaml
index 308aeec..608d16f 100644
--- a/dependencies.yaml
+++ b/dependencies.yaml
@@ -17,7 +17,7 @@
 # under the License.
 #
 
-pulsar-cpp: 4.1.0
+pulsar-cpp: 4.2.0
 pybind11: 3.0.1
 # The OpenSSL dependency is only used when building Python from source
 openssl: 1.1.1q