Fix broken `.flake8` config in template

[NiklasRosenstein]

A newer version of flake8 complains about a comment on the same line as data in the config file.

Example:

[flake8]
max-line-length = 120
# Black can yield formatted code that triggers these Flake8 warnings.
ignore=
    W503, # line break before binary operator
    W504, # line break after binary operator

Fixed:

[flake8]
max-line-length = 120
# Black can yield formatted code that triggers these Flake8 warnings.
ignore=
    # line break before binary operator
    W503,
    # line break after binary operator
    W504,

[NiklasRosenstein]

Actually this is already fixed, I was just running an older version of Slap.