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/__main__.py

@@ -36,7 +36,7 @@ config_path = Path(args.config or os.environ.get("OMNIBOT_CONFIG", "config.toml"
 config = ServerConfig()
 
 try:
-    with open(config_path) as fp:
+    with open(config_path, 'rb') as fp:
         config.load(fp)
 except FileNotFoundError:
     print(f"ERROR: config file not found: {config_path}", file=sys.stderr)