docs: align ticker latency wording with 10 ticks/sec default

[NikolayS]

Summary

Updates remaining docs wording that still described the production ticker as pgque.ticker() every second or used legacy force_tick wording in the snapshot-rule path.

The docs now consistently distinguish:

• default pg_cron path: one 1-second cron slot runs pgque.ticker_loop()
• actual default tick cadence: tick_period_ms = 100 → 10 ticks/sec
• external scheduler path: caller chooses how often to call pgque.ticker()
• canonical manual helper: force_next_tick() (force_tick() remains alias)

Test

• git diff --check
• grep for stale phrases: up to 1s, up to one second, calls .*ticker.* every second, force_tick.*ticker.*receive

Docs-only change.