Update docs/salt-server-list.rst (#570)

Co-authored-by: ewdurbin <ewdurbin@users.noreply.github.com>

Author: github-actions[bot]

docs/salt-server-list.rst

@@ -23,7 +23,7 @@
    "lb-1.nyc1.psf.io", "Load balancer", "Infrastructure Staff", "Ubuntu-24.04", "nyc1"
    "mail.ams1.psf.io", "Mail and mailman server", "postmasters", "Ubuntu-14.04", "ams1"
    "moin.nyc1.psf.io", "Hosts moin sites for wiki.python.org, wiki.jython.org", "lemburg", "Ubuntu-20.04", "nyc1"
-   "planet.nyc1.psf.io", "Planet Python", "benjamin", "Ubuntu-18.04", "nyc1"
+   "planet.nyc1.psf.io", "Planet Python", "benjamin", "Ubuntu-24.04", "nyc1"
    "pythontest.nyc3.psf.io", "Test resources for CPython's test suite.", "Infrastructure Staff", "Ubuntu-24.04", "nyc3"
    "salt.nyc1.psf.io", "Salt server", "Infrastructure Staff", "Ubuntu-20.04", "nyc1"