*: un-split strings across lines

*: un-split strings across lines

Remove mid-string line breaks, cf. workflow doc:

  .. [#tool_style_conflicts] For example, lines over 80 characters are allowed
     for text strings to make it possible to search the code for them: please
     see `Linux kernel style (breaking long lines and strings)
     <https://www.kernel.org/doc/html/v4.10/process/coding-style.html#breaking-long-lines-and-strings>`_
     and `Issue #1794 <https://github.com/FRRouting/frr/issues/1794>`_.

Scripted commit, idempotent to running:
```
python3 tools/stringmangle.py --unwrap `git ls-files | egrep '\.[ch]$'`
```

Signed-off-by: David Lamparter <equinox@diac24.net>