Target py3.8+ for black (#15583)

pyproject.toml

diff --git a/pyproject.toml b/pyproject.toml
index 0f2712b..1fc52df 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -17,7 +17,7 @@
 
 [tool.black]
 line-length = 99
-target-version = ["py37", "py38", "py39", "py310", "py311"]
+target-version = ["py38", "py39", "py310", "py311"]
 skip-magic-trailing-comma = true
 force-exclude = '''
 ^/mypy/typeshed|