TPA-RFC-77: clarifications

Here, we clarify the title to disambiguate with the weirdly similarly named "Puppet Merge Request Workflow" RFC.

We are also a bit more explicit in somes places, for example:

• we assume we might need to update 3rdparty modules in Tails
• we do not assume we switch to a g10k monorepo and instead refer to the related issue

See: team#41948 (closed)