[ZEPPELIN-6713] Stabilize editor blur E2E assertion

[voidmatcha]

What is this PR for?

NB-PARITY-003 can fail intermittently when Monaco's suggestion widget is open because the first Escape dismisses the widget instead of removing editor focus.

This PR makes the assertion deterministic by dismissing the suggestion widget first, waiting for it to close, and then pressing Escape again to blur the editor.

What type of PR is it?

Bug Fix

What is the Jira issue?

ZEPPELIN-6713

How should this be tested?

CI=true PLAYWRIGHT_BASE_URL=http://127.0.0.1:8081 npm exec -- playwright test \
  e2e/tests/notebook/paragraph/paragraph-functionality.spec.ts \
  --grep @NB-PARITY-003 \
  --project=chromium \
  --project=firefox \
  --project=webkit \
  --repeat-each=100 \
  --retries=0 \
  --workers=3 \
  --no-deps

The test passed 100 times on each browser without retries:

• Chromium: 100/100
• Firefox: 100/100
• WebKit: 100/100
• Total: 300/300

Questions

• Does the license file need updating? No
• Is there breaking changes for older versions? No
• Does this need documentation? No

[voidmatcha]

Merged into master (156cdd1).