pyproject.toml: Set target-version to py39 to match comment.

Author: schwehr

pyproject.toml

@@ -2,7 +2,6 @@
 requires = ["setuptools"]
 build-backend = "setuptools.build_meta"
 
-
 [tool.ruff]
 # Exclude a variety of commonly ignored directories.
 exclude = [
@@ -39,7 +38,7 @@ line-length = 88
 indent-width = 4
 
 # Assume Python 3.9
-target-version = "py37"
+target-version = "py39"
 
 [tool.ruff.lint]
 # Enable Pyflakes (`F`) and a subset of the pycodestyle (`E`)  codes by default.
@@ -66,8 +65,6 @@ skip-magic-trailing-comma = false
 # Like Black, automatically detect the appropriate line ending.
 line-ending = "auto"
 
-
-
 [tool.pylint.MASTER]
 load-plugins=[
     "pylint_per_file_ignores",