apacheGH-40974: [CI][Python] CI failures on Python builds due to pyte…

…st_cython (apache#40975)

### Rationale for this change

We are seeing sporadic CI failures on Python builds due to `pytest_cython`.

### What changes are included in this PR?

Upper pin of 0.3.0 added for `pytest-cython`.

### Are these changes tested?

With a green CI.

### Are there any user-facing changes?

No.
* GitHub Issue: apache#40974

Authored-by: AlenkaF <frim.alenka@gmail.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>

ci/conda_env_sphinx.txt

@@ -29,5 +29,8 @@ sphinx-copybutton
 sphinxcontrib-jquery
 sphinx==6.2
 # Requirement for doctest-cython
-pytest-cython
+# Needs upper pin of 0.3.0, see:
+# https://github.com/lgpage/pytest-cython/issues/67
+# With 0.3.* bug fix release, the pin can be removed
+pytest-cython==0.2.2
 pandas