remove makeStringStandinPromise

[turadg]

What is the Problem Being Solved?

kmarshall has a hack:

agoric-sdk/packages/kmarshal/src/kmarshal.js

Lines 41 to 45 in bfb7cdc

	// TODO This Bizarro world hack is only for the version of Endo that
	// agoric-sdk currently depends on, and is already inconsistent with
	// the "current" endo. Once agoric-sdk depends only on the next endo,
	// we should delete this code, and rename `makeStringStandinPromise`
	// above to `makeStandinPromise`.

That's working around an Endo version compatibility. Once we don't need that anymore we should remove it to reduce complexity (and questions about when to remove the hack).

Description of the Design

First verify that with current agoric-sdk line 89 at

agoric-sdk/packages/kmarshal/src/kmarshal.js

Line 89 in bfb7cdc

return [makeStringStandinPromise, getStringStandinPromiseTag];

is executed

Add tests that would fail if it weren't

Remove the hack

Security Considerations

Scaling Considerations

Test Plan

Upgrade Considerations