Pin geth docker version to v1.9.18

[ryanio]

Description

Currently ci is failing in trying to set up a geth instance for the e2e tests.

This PR tests pinning the geth version for geth-dev-assistant to 1.9.18 to see if the issue is something in the latest 1.9.19 release.

E2E: geth insta-mining (requires docker) 
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
 
> Pulling ethereum/client-go:stable
> ⚠️  Launching ethereum/client-go:stable as a background process. ⚠️ 
> ⚠️  Run docker stop geth-client when you are finished testing.   ⚠️
> Waiting for geth to launch... (10 sec maximum).
> Timed out while waiting for geth to launch.
  + Use --sleep <sec> to increase the wait time.
  + Use --interactive to see any errors geth may be throwing.

geth-client
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! web3.js@ test:e2e:geth:insta: `./scripts/e2e.geth.instamine.sh`
npm ERR! Exit status 1

Type of change=

• ci fix

[coveralls]

Coverage remained the same at 85.343% when pulling 13a3faf on pin-geth-1.9.18 into 0151821 on 1.x.

[ryanio]

Running geth-dev-assistant with --interactive outputs:

npx geth-dev-assistant --accounts 1 --tag 'stable' --interactive
> Pulling ethereum/client-go:stable
> ⚠️  Launching ethereum/client-go:stable as a background process. ⚠️
> ⚠️  Run docker stop geth-client when you are finished testing.   ⚠️
> Waiting for geth to launch... (10 sec maximum).

Geth reported error: INFO [08-17|17:38:55.025] Starting Geth in ephemeral dev mode...

So it must be getting confused that "Starting Geth in ephemeral dev mode..." message is coming through stderr, but according to https://github.com/cgewecke/geth-dev-assistant/blob/master/lib/app.js#L40-L51 if run without the --interactive flag, it shouldn't exit the process, so not exactly sure.

[GregTheGreek]

This LGTM until we update the upstream repo. I've found the probable cause, and looking at a patch. May need to fork if @cgewecke isn't around to merge it.