some tests with approved stubs have the wrong error

for example, the testLimitLegacyStubErrorVolume test:
https://github.com/python/mypy/blob/bd530392cdbe444c63cc21820ad7b9748ea9c816/test-data/unit/check-modules.test#L3015-L3018

since certifi is an approved stub, it should instead suggest installing them, like it does here:

>mypy -c "import certifi"
<string>:1: error: Library stubs not installed for "certifi" (or incompatible with Python 3.10)  [import]
<string>:1: note: Hint: "python3 -m pip install types-certifi"
<string>:1: note: (or run "mypy --install-types" to install all missing stub packages)
<string>:1: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
Found 1 error in 1 file (checked 1 source file)

but for some reason, these tests (and also the playground) don't do that

test-data/unit/check-modules.test の testLimitLegacyStubErrorVolume 周辺から始め、そこで期待されるエラーを issue の certifi の例と比較します。mypy/stubinfo.py の approved-stub エントリを読み、提供された mypy コマンドで動作を再現します。影響を受けるテストで approved stubs が一貫してそれぞれの types package のインストールを示唆し、playground の動作もそのとおりになることが完了の条件です。