edit_bot_modal: Fix puppeteer test flake.
edit_bot_modal: Fix puppeteer test flake.

This replaces the old way of waiting for the modal to be
hidden or shown with micromodal-specific ones.

kou/zulip,kou/zulip,eeshangarg/zulip,zulip/zulip,eeshangarg/zulip,andersk/zulip,rht/zulip,andersk/zulip,zulip/zulip,kou/zulip,zulip/zulip,eeshangarg/zulip,zulip/zulip,zulip/zulip,rht/zulip,andersk/zulip,rht/zulip,rht/zulip,andersk/zulip,eeshangarg/zulip,kou/zulip,andersk/zulip,zulip/zulip,rht/zulip,zulip/zulip,kou/zulip,kou/zulip,andersk/zulip,rht/zulip,eeshangarg/zulip,eeshangarg/zulip,kou/zulip,rht/zulip,eeshangarg/zulip,andersk/zulip