Feature examples removal. Compatibility with official gherkin

[olegpidsadnyi]

Gherkin 6 is becoming more complex. In order to be compatible with all the changes like multiple scenario examples we should remove our own complexity.
The spirit of pytest-bdd 6 would be gherkin compatibility.
This PR is removing the examples on the feature level.

[codecov]

Codecov Report

Merging #490 (cc528b9) into master (f4ed62d) will decrease coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #490      +/-   ##
==========================================
- Coverage   95.91%   95.86%   -0.05%     
==========================================
  Files          49       49              
  Lines        1640     1621      -19     
  Branches      179      177       -2     
==========================================
- Hits         1573     1554      -19     
  Misses         41       41              
  Partials       26       26              

Impacted Files	Coverage Δ
tests/feature/test_outline.py	100.00% <ø> (ø)
pytest_bdd/__init__.py	100.00% <100.00%> (ø)
pytest_bdd/parser.py	99.53% <100.00%> (-0.01%)	⬇️
pytest_bdd/scenario.py	91.56% <100.00%> (-0.11%)	⬇️

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