[CI] PyPy tests are slow again

[HaoZeke]

On PyPy, test_run.py::test_run_spec is significantly slower than the other tests. Here are the times for the top 5 tests on each run:

ubuntu-latest, pypy-3.11

146.00s call     test/test_run.py::test_run_spec
58.15s call     test/test_continuous.py::test_continuous
45.38s call     test/test_run.py::test_set_commit_hash
44.01s call     test/test_run.py::test_env_matrix_value
32.66s call     test/test_run.py::test_return_code

ubuntu-latest, 3.8

72.77s call     test/test_run.py::test_run_spec
60.80s call     test/test_find.py::test_find
47.45s call     test/test_workflow.py::test_run_publish
30.69s call     test/test_continuous.py::test_continuous
26.77s call     test/test_run.py::test_parallel

ubuntu-latest, 3.12

78.76s call     test/test_run.py::test_run_spec
62.91s call     test/test_find.py::test_find
32.17s call     test/test_continuous.py::test_continuous
28.23s call     test/test_run.py::test_parallel
25.39s call     test/test_run.py::test_env_matrix_value

macos-13, pypy-3.11

265.83s call     test/test_run.py::test_run_spec
132.88s call     test/test_continuous.py::test_continuous
96.61s call     test/test_run.py::test_env_matrix_value
90.89s call     test/test_run.py::test_set_commit_hash
73.53s call     test/test_profile.py::test_profile_python_commit

macos-13, 3.8

138.64s call     test/test_workflow.py::test_run_publish
113.98s call     test/test_run.py::test_run_spec
91.93s call     test/test_find.py::test_find
77.43s call     test/test_run.py::test_parallel
60.98s call     test/test_continuous.py::test_continuous

macos-13, 3.12

137.96s call     test/test_find.py::test_find
136.74s call     test/test_run.py::test_run_spec
82.01s call     test/test_continuous.py::test_continuous
55.19s call     test/test_run.py::test_parallel
49.24s call     test/test_run.py::test_env_matrix_value

Originally posted by @mattip in https://github.com/airspeed-velocity/asv/issues/1512#issuecomment-3178137988