Update ep_weave to etherpad 3 based image

[yacchin1205]

Summary

• Update the images/ep_weave/ep_weave submodule to the latest upstream main, which builds on etherpad/etherpad:3 and no longer runs npm pack during the image build. Recent etherpad images dropped npm in favor of pnpm, so the previous build had started failing with npm: not found (see the CI failure on Add nginx ACME module support #47).
• Remove the ETHERPAD_IMAGE_TAG=develop build arg override so the image tag follows the upstream Dockerfile default (3) instead of the floating develop tag.
• Disable the newly bundled ep_webrtc plugin in local.json, matching the upstream demo settings.

CI has been verified on my fork: yacchin1205#1