Bump pdf2image from 1.13.1 to 1.14.0 in /cvat/requirements (#2076)

Bumps [pdf2image](https://github.com/Belval/pdf2image) from 1.13.1 to 1.14.0.
- [Release notes](https://github.com/Belval/pdf2image/releases)
- [Commits](https://github.com/Belval/pdf2image/compare/v1.13.1...v1.14.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

cvat/requirements/base.txt

@@ -33,7 +33,7 @@ djangorestframework==3.11.1
 Pygments==2.6.1
 drf-yasg==1.17.1
 Shapely==1.7.1
-pdf2image==1.13.1
+pdf2image==1.14.0
 pascal_voc_writer==0.1.4
 django-rest-auth[with_social]==0.9.5
 cython==0.29.21