build(deps): replace the deprecated pysnmp-lextudio with pysnmp>=7.1 (#5470)

#5470 "pysnmp-lextudio is deprecated: every startup logs a RuntimeWarning".

Dependency change: the [snmp] extra now installs `pysnmp>=7.1` instead of
`pysnmp-lextudio>=6.2`. pysnmp is the same lextudio lineage under its maintained
name; the 7.1 floor is because below 7 the name is the abandoned 4.x line with
no asyncio API. The poller already finds either API shape (_api(), the engine
close probes), so no code changes; its docstring now names what the image ships.
Approved by the operator 2026-10-09 ("yes please do the swap").

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

pyproject.toml

@@ -28,7 +28,10 @@ ldap = [
     "ldap3>=2.9",
 ]
 snmp = [
-    "pysnmp-lextudio>=6.2",
+    # The maintained pysnmp (lextudio's lineage, which took over the name).
+    # Floor 7.1: below 7 that name is the abandoned 4.x line, which has no
+    # asyncio API (#5470; the poller uses pysnmp.hlapi.v3arch.asyncio).
+    "pysnmp>=7.1",
 ]
 # Batteries-included Ansible (bundles the common community collections) for the
 # playbook runner. Installed into the image via Dockerfile `pip install .[ansible]`.