Deduplicate the tox envlist and pin the pytest 8.2/8.3/9.0 factors

Merge the two overlapping envlist rows: the only reason for the split
is that pytest 7.0-7.2 do not support python 3.12+. Env coverage is
unchanged (verified with `tox -l` before/after).

The pytest8.2 and pytest8.3 factors had no matching pin in the deps
section, so those envs silently installed the latest pytest and just
duplicated pytestlatest. Pin them, and add a pytest9.0 factor now that
pytest 9 is out.

Author: Pierre-Sassoulas

tox.ini

@@ -1,6 +1,7 @@
 [tox]
-envlist = py{3.10,3.11}-pytest{7.0,7.1,7.2,7.3,7.4,8.0,8.1,8.2,8.3,latest}-gherkin_official{29,30,32,33,34,35,36,37,latest}-coverage
-          py{3.12,3.13,3.14}-pytest{7.3,7.4,8.0,8.1,8.2,8.3,latest}-gherkin_official{29,30,32,33,34,35,36,37,latest}-coverage
+# pytest 7.0-7.2 do not support python 3.12+
+envlist = py{3.10,3.11}-pytest{7.0,7.1,7.2}-gherkin_official{29,30,32,33,34,35,36,37,latest}-coverage
+          py{3.10,3.11,3.12,3.13,3.14}-pytest{7.3,7.4,8.0,8.1,8.2,8.3,9.0,latest}-gherkin_official{29,30,32,33,34,35,36,37,latest}-coverage
           py3.15-pytestlatest-gherkin_officiallatest-coverage
           py3.12-pytestlatest-xdist-coverage
           mypy
@@ -22,6 +23,9 @@ deps =
     gherkin_official29: gherkin-official~=29.0.0
 
     pytestlatest: pytest
+    pytest9.0: pytest~=9.0.0
+    pytest8.3: pytest~=8.3.0
+    pytest8.2: pytest~=8.2.0
     pytest8.1: pytest~=8.1.0
     pytest8.0: pytest~=8.0.0
     pytest7.4: pytest~=7.4.0