Removed more deprecated code

[tpazderka]

• Any changes relevant to users are recorded in the CHANGELOG.md.
• The documentation has been updated, if necessary.
• New code is annotated.
• Changes are covered by tests.

---

[codecov-io]

Codecov Report

Merging #677 into master will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #677      +/-   ##
==========================================
+ Coverage    62.5%   62.54%   +0.04%     
==========================================
  Files          62       62              
  Lines       11382    11355      -27     
  Branches     2000     1996       -4     
==========================================
- Hits         7114     7102      -12     
+ Misses       3693     3679      -14     
+ Partials      575      574       -1

Impacted Files	Coverage Δ
src/oic/utils/http_util.py	69.27% <ø> (+1.29%)	⬆️
src/oic/oic/provider.py	68.12% <ø> (-0.14%)	⬇️
src/oic/utils/authn/client.py	69.41% <ø> (+1.06%)	⬆️

---

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 91a7d74...fcf78d3. Read the comment docs.

[schlenk]

LGTM