Don't installs self in tox deps

[hroncok]

Tox already does that by default.

In Fedora, when we build RPM packages,
we use a tox plugin that installs the test requirements from RPMs.
It does not know how to install the package we are building.

[codecov]

Codecov Report

Merging #319 (520e5fb) into master (b2ea792) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #319   +/-   ##
=======================================
  Coverage   91.28%   91.28%           
=======================================
  Files          20       20           
  Lines        1102     1102           
  Branches      237      237           
=======================================
  Hits         1006     1006           
  Misses         54       54           
  Partials       42       42           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update b2ea792...520e5fb. Read the comment docs.