Update coverage.py concurrency configuration

2effdb0
fastapi/fastapi#3557
nedbat/coveragepy#1082
https://coverage.readthedocs.io/en/6.2/config.html

pyproject.toml had an unnecessary `--concurrency=multiprocessing` config
setting, which had been added in 2effdb0 to avoid "very wrong results,"
as worded in the coverage.py docs. Tests do use the multiprocessing
package, but don't actually start multiple processes, so the setting is
not needed.

After updating to coverage.py 6.2, reports incorrectly showed FastAPI
and Starlette TestClient route code as uncovered, when it actually was.
Removing the concurrency setting from pyproject.toml resolves the issue.

pyproject.toml

@@ -1,6 +1,3 @@
-[tool.coverage.run]
-concurrency = ["multiprocessing"]
-
 [tool.isort]
 profile = "black"
 src_paths = ["inboard", "tests"]