CI: Simplify Pulsar version string parsing in tests.yml

[DeeDeeG]

Pursuant to a discussion on Discord: https://discord.com/channels/992103415163396136/1186519181592633434/1186570766343487528

I found a simpler, arguably more-readable way to parse the output of pulsar --version into just the Pulsar version (digits and dots).

After going back and forth a bit in Discord, this solution was requested to be posted as a PR.

I figured I'd go ahead and post it real quick before I forget and have to remind myself of the details tomorrow. So, here it is!

cc @confused-Techie

[confused-Techie]

Thanks for posting this!
Especially since we can see this works right away in our tests, looks like we should be good to merge right away.

Since while the previous solution worked the majority of the time, we did get strange behavior on the latest release turning the content into a date, rather than text, so this seems to be an awesome solution.