Bump ng2-pdf-viewer from 9.0.0 to 9.1.0 in /src-ui

Bump ng2-pdf-viewer from 9.0.0 to 9.1.0 in /src-ui

Bumps [ng2-pdf-viewer](https://github.com/VadimDez/ng2-pdf-viewer) from 9.0.0 to 9.1.0.
- [Release notes](https://github.com/VadimDez/ng2-pdf-viewer/releases)
- [Changelog](https://github.com/VadimDez/ng2-pdf-viewer/blob/master/CHANGELOG.md)
- [Commits](https://github.com/VadimDez/ng2-pdf-viewer/compare/9.0.0...9.1.0)

---
updated-dependencies:
- dependency-name: ng2-pdf-viewer
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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