Clarify that deleteDatabase() blocks until open connections close

[vamshikrishnaramasamy]

Fixes #20368.

The page mentions that open connections receive a versionchange event, but doesn't explain the consequence: the deletion will not complete (and success will not fire) while any connection to the database is still open. This is a common source of confusion — people wait for onsuccess that never comes because a connection is left open.

This expands the existing sentence to spell out that:

• the deletion stays pending until every connection closes;
• a blocked event is fired on the request if a connection doesn't close in response to versionchange;
• closing connections (e.g. via IDBDatabase.close()) lets the deletion proceed.

This matches the spec's database-deletion steps and the behavior @evanstade quoted on the issue.

[github-actions]

Preview URLs (1 page)

• /en-US/docs/Web/API/IDBFactory/deleteDatabase