Update instructions for maven-deployment example

[dfuenzalida]

• Remove the HTTP port: As per the latest change in application.properties the web app won't listen on port 8080 but on port 80 which is the default and can be removed
• Update the plugin version, add a link to the Maven Central search site: https://search.maven.org/

Purpose

• Update outdated/misleading instructions

Does this introduce a breaking change?

[ ] Yes
[x] No

Pull Request Type

What kind of change does this Pull Request introduce?

[ ] Bugfix
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[x] Documentation content changes
[ ] Other... Please describe:

Other Information