fix: fix misleading CLI help text (#76)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Style**
* Updated user-facing labels and descriptions to refer to "plugin
settings" instead of "executor settings" for improved clarity.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: johanneskoester

src/snakemake_interface_common/plugin_registry/plugin.py

@@ -96,7 +96,7 @@ def support_tagged_values(self) -> bool:
         return False
 
     def has_settings_cls(self) -> bool:
-        """Determine if a plugin defines custom executor settings"""
+        """Determine if a plugin defines custom settings"""
         return self.settings_cls is not None
 
     def get_settings_info(self) -> List[Dict[str, Any]]:
@@ -151,7 +151,7 @@ def register_cli_args(self, argparser: "ArgumentParser") -> None:
                     self.name, "Fields of ExecutorSettings must have a default value."
                 )
 
-        settings = argparser.add_argument_group(f"{self.name} executor settings")
+        settings = argparser.add_argument_group(f"{self.name} plugin settings")
 
         for thefield in fields(params):
             prefixed_name = self._get_prefixed_name(thefield.name).replace("-", "_")