[PATCH v2] completion: Make sed command that generates config-list.h portable.

The OpenBSD 'sed' command does not support '\n' to represent newlines in sed expressions. This leads to the follow compiler error:

    In file included from builtin/help.c:15:
    ./config-list.h:282:18: error: use of undeclared identifier 'n'
            "gitcvs.dbUser",n       "gitcvs.dbPass",
                            ^
    1 error generated.
    gmake: *** [Makefile:2821: builtin/help.o] Error 1

We can use a backslash followed by a newline to fix this.

This portably issue was introduced in e1b81f54da (completion: take into account the formatting backticks for options, 2025-03-19)

Signed-off-by: Collin Funk <collin.funk1@gmail.com>
---
 generate-configlist.sh | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)