don't require importlib-metadata with python 3.8 (#1586)

This is probably only a typo.

`importlib-metadata` was included in the standard library, so the requirement should be `< 3.8`, not `<= 3.8`.

pyproject.toml

@@ -55,7 +55,7 @@ keyring = [
 ]
 ]
 # Use subprocess32 for Python 2.7 and 3.4
 # Use subprocess32 for Python 2.7 and 3.4
 subprocess32 = { version = "^3.5", python = "~2.7 || ~3.4" }
 subprocess32 = { version = "^3.5", python = "~2.7 || ~3.4" }
-importlib-metadata = {version = "^0.23", python = "<=3.8"}
+importlib-metadata = {version = "^0.23", python = "<3.8"}
 
 
 [tool.poetry.dev-dependencies]
 [tool.poetry.dev-dependencies]
 pytest = "^4.1"
 pytest = "^4.1"