Complete type annotations

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

conftest.py

@@ -7,11 +7,11 @@
 ]
 
 
-def pytest_configure():
+def pytest_configure() -> None:
     remove_importlib_metadata()
 
 
-def remove_importlib_metadata():
+def remove_importlib_metadata() -> None:
     """
     Because pytest imports importlib_metadata, the coverage
     reports are broken (#322). So work around the issue by

exercises.py

@@ -1,32 +1,32 @@
 from pytest_perf.deco import extras
 
 
-@extras('perf')
-def discovery_perf():
+@extras('perf')  # type: ignore[misc]
+def discovery_perf() -> None:
     "discovery"
     import importlib_metadata  # end warmup
 
     importlib_metadata.distribution('ipython')
 
 
-def entry_points_perf():
+def entry_points_perf() -> None:
     "entry_points()"
     import importlib_metadata  # end warmup
 
     importlib_metadata.entry_points()
 
 
-@extras('perf')
-def cached_distribution_perf():
+@extras('perf')  # type: ignore[misc]
+def cached_distribution_perf() -> None:
     "cached distribution"
     import importlib_metadata
 
     importlib_metadata.distribution('ipython')  # end warmup
     importlib_metadata.distribution('ipython')
 
 
-@extras('perf')
-def uncached_distribution_perf():
+@extras('perf')  # type: ignore[misc]
+def uncached_distribution_perf() -> None:
     "uncached distribution"
     import importlib
     import importlib_metadata