pyproject: allow pysnmp newer than 6.x

With the new asyncio based handling we can unlock the pysnmp dependency.
The lexstudio fork has also taken over maintenance of pysnmp on pypi, so
switch back to pysnmp.

Signed-off-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>

pyproject.toml

@@ -69,7 +69,7 @@ pyvisa = [
     "pyvisa>=1.11.3",
     "PyVISA-py>=0.5.2",
 ]
-snmp = ["pysnmp-lextudio>=4.4.12, <6"]
+snmp = ["pysnmp>6"]
 vxi11 = ["python-vxi11>=0.9"]
 xena = ["xenavalkyrie>=3.0.1"]
 deb = [
@@ -80,7 +80,7 @@ deb = [
     "onewire>=0.2",
 
     # labgrid[snmp]
-    "pysnmp-lextudio>=4.4.12, <6",
+    "pysnmp>6",
 ]
 dev = [
     # references to other optional dependency groups
@@ -114,7 +114,7 @@ dev = [
     "PyVISA-py>=0.5.2",
 
     # labgrid[snmp]
-    "pysnmp-lextudio>=4.4.12, <6",
+    "pysnmp>6",
 
     # labgrid[vxi11]
     "python-vxi11>=0.9",