Update to latest version of Pulsar `4.x`

[onobc]

Need to decide which version of Pulsar that Spring Pulsar 2.0.x should use.
The current version of Pulsar is 4.0.5.
The next minor release is 4.1.0 which seems like it may not be ready in time.

• Reach out to Pulsar folks and get a feel on when 4.1.0 is expected
• If ready in time, go w/ 4.1.0. If not ready in time, bump to latest patch of 4.0.x.