update Member Expectations to include project stewardship

[Trott]

This change replaces text about leadership's obligation to "protect" the
project with a hopefully-more-clear reference to project stewardship.
The use of "protect" suggests a defensive and adversarial stance.
Project stewardship, on the other hand, implies more of a caretaker
stance. It still involves ensuring the project's well-being, but does
not assume that there is a fight to be had.

@nodejs/tsc @nodejs/community-committee

[Trott]

(The bit about an obligation to treat others respectfully was removed because it's already in the document as "Treat all community members with respect, consideration, and highest standards of ethical conduct." and it seems to be otherwise bolted on to this paragraph. The rest of the paragraph fits in with project stewardship, but only indirectly with treating others with respect.)

[MylesBorins]

I've added tsc-review

[mhdawson]

Somehow I missed adding my last comment which was that

When someone takes on a leadership role, they take on additional obligations of
project stewardship. 

does not seem to fit into the flow so I'd just remove the whole line and the paragraph break. However, I'll leave that up to you to decide if you want to do that.

[Trott]

@mhdawson I'd be OK with dropping that sentence as you suggest. The document as a whole works just fine without it.