[OSPO Book] Merge sections about starting and sustaining OSPOs

[cornelius]

Chapter 2 currently has separate sections about the reasons to start and OSPO and to sustain it.

I perceive that as confusing. An OSPO as an organizational structure is inherently meant to be a permanent thing. Its responsibilities such as managing compliance, mitigating security risks, or connecting to the open source community are all long-term activities without a defined end. So I can't really think of a scenario where it makes sense to start an OSPO without sustaining it.

It would be clearer to combine the sections into one, maybe under the title "Reasons for having an OSPO" or something like that.

Part of the confusion might actually come from the misnomer of Open Source Program Office. A program mostly has a natural end and the term is often used in organizations to name time-limited initiatives. So having this as part of the name might create wrong assumptions. This part of the confusion I would rather address in a clarification of the naming of an OSPO-like organizational structure than letting it structure the reasoning for having an OSPO.

[anajsana]

I've included this issue to review in the WG during our first contributors call this February 👍