security/gvm: Update to 21.4.0

The following ports part of security gvm were updated

security/gvmd: Update to 21.4.0
security/gvm-libs: Update to 21.4.0
security/openvas: Update to 21.4.0
security/py-ospd-openvas: Update to 21.4.0
security/py-ospd: Update to 21.4.0
security/greenbone-security-assistant: Update to 21.4.0
security/py-python-gvm: Update to 21.5.2
security/py-gvm-tools: Update to 21.6.0

Notable Changes in this Release

- All components and the feed support CVSSv3/CVSSv3.1
- GSA contains a new calculator for these CVSS versions
- Rework of the login page in GSA to have a better entry point into our software
- Dropped support for Internet Explorer
- Dropped support for Microsoft Edge <= 18
- Removed auto false positive feature
- Removed GMP scanner support
- Dropped dynamic severity classes
- Removed support for Python 3.5 and lower

PR:		254630 254632
Reported by:	Eirik Oeverby <ltning-freebsd at anduin.net>