BASH integration: No longer modify .bashrc to load shell integration

I think I have things setup robustly so that the shell integration
is loaded transparently via env vars and the normal bash startup files
are sourced, in the same way that vanilla bash does it. Let's hope I
haven't overlooked something.

kitty/main.py

@@ -30,7 +30,6 @@ from .options.types import Options
 from .options.utils import DELETE_ENV_VAR
 from .os_window_size import initial_window_size_func
 from .session import get_os_window_sizing_data
-from .shell_integration import setup_shell_integration
 from .types import SingleKey
 from .utils import (
     detach, expandvars, log_error, single_instance,
@@ -322,7 +321,6 @@ def setup_environment(opts: Options, cli_opts: CLIOptions) -> None:
         os.environ['KITTY_LISTEN_ON'] = cli_opts.listen_on
     env = opts.env.copy()
     ensure_kitty_in_path()
-    setup_shell_integration(opts, env)
     kitty_path = shutil.which('kitty')
     if kitty_path:
         child_path = env.get('PATH')