Fix all of github action workflows

[danielsagi]

Description

Made some changes to the workflows.

• Removed ubuntu16.04 from the test lists - deprecated by github.
• Removed editable install from requirements-dev
• Other minor changes to Makefile

Contribution checklist

• [ ] I have read the Contributing Guidelines.
• [ ] The commits refer to an active issue in the repository.
• [ ] I have added automated testing to cover this case.

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[codecov[bot]]

Codecov Report

Merging #481 (d50f78c) into main (473e4fe) will increase coverage by 0.99%. The diff coverage is 87.59%.

@@            Coverage Diff             @@
##             main     #481      +/-   ##
==========================================
+ Coverage   63.67%   64.66%   +0.99%     
==========================================
  Files          43       46       +3     
  Lines        2431     2502      +71     
==========================================
+ Hits         1548     1618      +70     
- Misses        883      884       +1     

Impacted Files	Coverage Δ
kube_hunter/modules/hunting/cves.py	78.09% <ø> (ø)
kube_hunter/modules/hunting/etcd.py	33.75% <ø> (ø)
kube_hunter/modules/hunting/kubelet.py	60.40% <ø> (ø)
kube_hunter/modules/hunting/proxy.py	48.43% <ø> (ø)
kube_hunter/modules/report/base.py	30.30% <ø> (ø)
kube_hunter/modules/report/plain.py	12.50% <0.00%> (ø)
kube_hunter/core/types/hunters.py	65.21% <65.21%> (ø)
kube_hunter/modules/hunting/apiserver.py	72.34% <71.42%> (+1.92%)	:arrow_up:
kube_hunter/core/events/types.py	82.81% <80.00%> (-0.39%)	:arrow_down:
kube_hunter/core/types/vulnerabilities.py	93.67% <93.67%> (ø)
... and 13 more

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