docs: drop the SQLite alternative from the Redis sidecar section

Redis-only now. The persist-or-not decision stays ephemeral (--save "")
vs persistent (--appendonly yes + ${MOUNTS_DIR}), and both caveats — the
~1s appendfsync everysec window and the not-backed-up dividing line —
are unchanged.

Signed-off-by: disqualifier <dev@disqualifier.me>

docs/deploy.md

@@ -268,13 +268,6 @@ durability changes.
     would actually hurt, it isn't queue or cache state — it's a system of record, and it
     belongs in Postgres (which *is* backed up), not a local mount.
 
-!!! tip "Sometimes you don't need Redis at all"
-    For the dead-simple case — **one process draining its own queue** — a **SQLite file**
-    under the mounts dir does the job with no extra container: atomic commits, crash-safe,
-    zero infra. Reach for Redis when it's actually doing queue *things* (multiple workers,
-    blocking pops, streams / consumer groups, pub/sub) or when it's already in your compose
-    for something else.
-
 ### The rules
 
 !!! danger "Don't do these"