Use "PT" and not "PST"

We use UTC as the timezone for engineering (for example production postmortems) and all cross-functional activities related to the monthly release. We use Pacific Time (PT) for all other uses since we are a San Francisco-based company. Please refer to time as "9:00 Pacific" or 9:00 PT. It isn't often necessary to specify whether a timezone is currently observing Daylight Saving Time, and such references are often incorrect, so prefer "PT" to "PDT" or "PST" unless you have a specific need to differentiate between PDT and PST.

Fix Company call section to use PT, and not PST

Review app: https://fix-pt-company-calls.about.gitlab-review.app/handbook/communication/index.html#company-call