Update to Python 3.12

* Remove toml dependency since that comes with Python as of 3.11
* Update toml usage to tomllib in config.py
* Update `with open(...)` for toml file reading to be 'rb'
* Update Pipfile.lock for locked dependencies to work with Python 3.12

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

omnibot/config.py

@@ -1,8 +1,7 @@
 import dataclasses
 from pathlib import Path
 from typing import IO, Any, Mapping, Sequence, Set
-
-import toml
+import tomllib
 
 
 PluginConfig = Mapping[str, Any]
@@ -34,7 +33,7 @@ class ServerConfig:
     loglevel: str | None = None
 
     def load(self, fp: IO[str]):
-        obj = toml.load(fp)
+        obj = tomllib.load(fp)
 
         if "server" not in obj:
             raise ConfigError("server", "must be present")