template: Ignore E704 in flake8 config

This is needed to make black 24.8 and flake8 play nicely with each
other, see
https://black.readthedocs.io/en/stable/guides/using_black_with_other_tools.html#e701-e704

copier-template/setup.cfg

@@ -4,5 +4,5 @@
 # E501: line too long, use B950 warning from flake8-bugbear instead
 # W503: line break before binary operator <https://github.com/psf/black/issues/52>
 select = C,E,F,W,B950
-ignore = E203,E231,E501,W503
+ignore = E203,E231,E501,E704,W503
 max-line-length = 88