Add pragma no cover to redis connection retry in conftest (#264)

The `except ConnectionError` in `_wait_for_redis` is a timing-dependent
branch that's essentially impossible to reliably hit in tests - it fires
when Redis hasn't started yet during container spinup. Marking it with
`pragma: no cover` to avoid flaky coverage.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: chrisguidry

tests/conftest.py

@@ -17,7 +17,6 @@
 from redis import ConnectionPool, Redis
 
 from docket import Docket, Worker
-
 from tests._key_leak_checker import KeyCountChecker
 
 REDIS_VERSION = os.environ.get("REDIS_VERSION", "7.4")
@@ -59,7 +58,7 @@ def _wait_for_redis(port: int) -> None:
             with _administrative_redis(port) as r:
                 if r.ping():  # type: ignore  # pragma: no branch
                     return
-        except redis.exceptions.ConnectionError:
+        except redis.exceptions.ConnectionError:  # pragma: no cover
             time.sleep(0.1)