Bump pyunpack from 0.1.2 to 0.2.1 in /cvat/requirements (#1743)

Bumps [pyunpack](https://github.com/ponty/pyunpack) from 0.1.2 to 0.2.1.
- [Release notes](https://github.com/ponty/pyunpack/releases)
- [Commits](https://github.com/ponty/pyunpack/compare/0.1.2...0.2.1)

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

@@ -10,7 +10,7 @@ Pillow==7.1.2
 numpy==1.18.5
 python-ldap==3.2.0
 pytz==2020.1
-pyunpack==0.1.2
+pyunpack==0.2.1
 rcssmin==1.0.6
 redis==3.2.0
 requests==2.24.0