CI: ruff: use 0.11.0 (Cannot use star annotation)

Ruff 0.11.1 is incorrectly printing the following types of errors:

pmb/helpers/logging.py:169:34: SyntaxError: Cannot use star annotation on Python 3.10 (syntax was added in Python 3.11)
    |
169 | def critical(msg: object, *args: str, **kwargs: Any) -> None:
    |                                  ^^^
170 |     logging.critical(msg, *args, **kwargs)
    |

But the code works fine in Python 3.10 (see pytest-python3.10 CI job).
This is a known upstream bug, pin to the previous version until it is
fixed.

Related: https://github.com/astral-sh/ruff/issues/16874
Part-of: !2578

.ci/ruff.sh

@@ -5,7 +5,9 @@
 if [ "$(id -u)" = 0 ]; then
 	set -x
 	apk -q add py3-pip
-	pip install --break-system-packages --no-warn-script-location ruff
+	# pin to ruff 0.11.0 until this is fixed:
+	# https://github.com/astral-sh/ruff/issues/16874
+	pip install --break-system-packages --no-warn-script-location ruff==0.11.0
 	exec su "${TESTUSER:-build}" -c "sh -e $0"
 fi