refactor: update pdfjs import and improve file filtering in electron-builder configuration

[beyondkmp]

…builder configuration

• Changed pdfjs import to a direct import from 'pdfjs-dist' for consistency across modules.
• Updated file filtering in electron-builder.yml to exclude all legacy files from pdfjs-dist instead of just specific ones.

What this PR does

Before this PR:

pdfjs没有复用

After this PR:
pdfjs复用，并用删除legacy/build

Fixes #

Why we need it and why it was done in this way

The following tradeoffs were made:

The following alternatives were considered:

Links to places where the discussion took place:

Breaking changes

If this PR introduces breaking changes, please describe the changes and the impact on users.

Special notes for your reviewer

Checklist

This checklist is not enforcing, but it's a reminder of items that could be relevant to every PR.
Approvers are expected to review this list.

• PR: The PR description is expressive enough and will help future contributors
• Code: Write code that humans can understand and Keep it simple
• Refactor: You have left the code cleaner than you found it (Boy Scout Rule)
• Upgrade: Impact of this change on upgrade flows was considered and addressed if required
• Documentation: A user-guide update was considered and is present (link) or not required. You want a user-guide update if it's a user facing feature.

Release note