Update minimum Python version for pylint (#10318)

This got missed during 4dfef13, and is needed to avoid Pylint
complaining about standard-library features that were added after the
minimum version it thinks we're on.

pyproject.toml

@@ -49,7 +49,7 @@ extension-pkg-allow-list = [
     "tweedledum",
 ]
 load-plugins = ["pylint.extensions.docparams", "pylint.extensions.docstyle"]
-py-version = "3.7"  # update it when bumping minimum supported python version
+py-version = "3.8"  # update it when bumping minimum supported python version
 
 [tool.pylint.basic]
 good-names = ["a", "b", "i", "j", "k", "d", "n", "m", "ex", "v", "w", "x", "y", "z", "Run", "_", "logger", "q", "c", "r", "qr", "cr", "qc", "nd", "pi", "op", "b", "ar", "br", "p", "cp", "ax", "dt", "__unittest", "iSwapGate", "mu"]