build: avoid failure to delete Symbol.dispose using ses 0.18.5

[dckc]

fixes #50
fixes #43

to test

Run thru the getting started process but use the dc-dispose-fix branch at the yarn create step:

yarn create @agoric/dapp --dapp-template dapp-offer-up --dapp-branch dc-dispose-fix demo

diagnosis: SES 0.18.4 and node v18.19.0 don't get along

We have seen some issues near node v18.19.0:

• Node 18.19 breaks release-mainnet1B branch agoric-sdk#8599

And now that version is in the ghcr.io/agoric/agoric-sdk:39 image used in this dapp by way of agoric-3-proposals:

$ docker run --rm -ti --entrypoint=/bin/bash ghcr.io/agoric/agoric-sdk:39 
root@73e3f8a55f2a:~# node --version
v18.19.0

https://github.com/Agoric/agoric-sdk/blob/45a954cbcbb083e756e8244240818632c1277396/packages/deployment/Dockerfile.sdk#L33-L36

that takes us to...

https://github.com/nodejs/docker-node/blob/f416b53801a9d49d6ce6b2c038c8bc9ed93625dd/18/bullseye/Dockerfile#L6

ENV NODE_VERSION 18.19.0

treatment: use 0.18.5

including a relevant fix: 9fb1242

reportedly 0.18.8 should work, but I haven't tested it.