Fix invalid version specifier, which newer setuptools reject
outright:
    error in etask setup command: 'python_requires' must be a
    string containing valid version specifiers; Invalid specifier:
    '>=3.6.*'

Strip the bogus trailing wildcard so the declaration is a valid
specifier again.

--- a/src/etask/setup.py
+++ b/src/etask/setup.py
@@ -21,7 +21,7 @@
     url="https://gitlab.com/xgqt/python-etask",
     license="GPL-2-or-later",
     keywords="emacs",
-    python_requires=">=3.6.*",
+    python_requires=">=3.6",
     install_requires=["colorama"],
     packages=["etask"],
     include_package_data=True,