Restore normal python versions declaration in tox

[yakky]

Description

Drop the dot in tox environment definitions by using generic python environment in GA

References

Fix #606

Checklist

• I have read the contribution guide
• Code lint checked via inv lint
• changes file included (see docs)
• Usage documentation added in case of new features
• Tests added

[codecov]

Codecov Report

Merging #609 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #609   +/-   ##
========================================
  Coverage    93.84%   93.84%           
========================================
  Files           22       22           
  Lines         1024     1024           
  Branches       135      135           
========================================
  Hits           961      961           
  Misses          25       25           
  Partials        38       38           

Flag	Coverage Δ
#unittests	93.84% <ø> (ø)

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[coveralls]

Coverage remained the same at 96.414% when pulling e704bc5 on bugfix/issue-606-tox-versions into 23c4101 on develop.