chore: [pre-commit.ci] pre-commit autoupdate (#2240)

* Update pre-commit hooks:
   - github.com/astral-sh/ruff-pre-commit: v0.0.270 → v0.0.276
   - github.com/asottile/blacken-docs: 1.13.0 → 1.14.0
   - github.com/pre-commit/mirrors-mypy: v1.3.0 → v1.4.1
   - github.com/codespell-project/codespell: v2.2.4 → v2.2.5
* Add ClassVar type hint and apply isort.
   - Avoid RUF012 Mutable class attributes should be annotated with `typing.ClassVar`.

Author: pre-commit-ci[bot]

.pre-commit-config.yaml

@@ -27,7 +27,7 @@ repos:
       exclude: ^validation/|\.dtd$|\.xml$
 
 - repo: https://github.com/astral-sh/ruff-pre-commit
-  rev: "v0.0.270"
+  rev: "v0.0.276"
   hooks:
     - id: ruff
       args: ["--fix", "--show-fixes"]
@@ -38,13 +38,13 @@ repos:
     - id: black-jupyter
 
 -   repo: https://github.com/asottile/blacken-docs
-    rev: 1.13.0
+    rev: 1.14.0
     hooks:
     - id: blacken-docs
       additional_dependencies: [black==23.3.0]
 
 -   repo: https://github.com/pre-commit/mirrors-mypy
-    rev: v1.3.0
+    rev: v1.4.1
     # check the oldest and newest supported Pythons
     hooks:
       - &mypy
@@ -62,11 +62,11 @@ repos:
     rev: 1.7.0
     hooks:
     - id: nbqa-ruff
-      additional_dependencies: [ruff==0.0.270]
+      additional_dependencies: [ruff==0.0.276]
       args: ["--extend-ignore=F821,F401,F841,F811"]
 
 -   repo: https://github.com/codespell-project/codespell
-    rev: v2.2.4
+    rev: v2.2.5
     hooks:
     - id: codespell
       files: ^.*\.(py|md|rst)$

src/pyhf/workspace.py

@@ -5,14 +5,18 @@
 * the observed data (optional)
 * fit configurations ("measurements")
 """
+from __future__ import annotations
+
+import collections
+import copy
 import logging
+from typing import ClassVar
+
 import jsonpatch
-import copy
-import collections
-from pyhf import exceptions
-from pyhf import schema
-from pyhf.pdf import Model
+
+from pyhf import exceptions, schema
 from pyhf.mixins import _ChannelSummaryMixin
+from pyhf.pdf import Model
 
 log = logging.getLogger(__name__)
 
@@ -284,7 +288,7 @@ class Workspace(_ChannelSummaryMixin, dict):
     A JSON-serializable object that is built from an object that follows the :obj:`workspace.json` `schema <https://scikit-hep.org/pyhf/likelihood.html#workspace>`__.
     """
 
-    valid_joins = ['none', 'outer', 'left outer', 'right outer']
+    valid_joins: ClassVar[list[str]] = ['none', 'outer', 'left outer', 'right outer']
 
     def __init__(self, spec, validate: bool = True, **config_kwargs):
         """