Stop SyntaxWarnings because of some escaped blank

[hacklschorsch]

I see these often at the very beginning when running tests - I removed that backslash, but also, not so sure what I'm doing here. @crwood is removing these okay? Why are they there in the first place?

    _zkapauthorizer/replicate.py:393: SyntaxWarning: invalid escape sequence '\ '
    _zkapauthorizer/replicate.py:490: SyntaxWarning: invalid escape sequence '\ '

[crwood]

Ah, yes, this was a change introduced in Python 3.12 (which raises a SyntaxWarning for invalid escape sequences instead of a DeprecationWarning). See here or here

The usual/recommended way to fix this is by making the docstring into a "raw" string (i.e., adding an r prefix to the to the first line of the docstring by changing """... to r"""...); as per PEP 257:

Use r"""raw triple double quotes""" if you use any backslashes in your docstrings.

Removing it also works, but depending on what's rendering those docstrings (if they're being rendered by anything?), you might see an extra space where there was no extra space before.

[hacklschorsch]

Thank you for your review @crwood !