systemd: Fix importd requirements comment

systemd: Fix importd requirements comment

The comment above the importd config states curl, which does not
exist in PACKAGECONFIG. Adding it results in the following error
(and then misleading compilation failures):

    WARNING: systemd-1_244.5-r0 do_configure: QA Issue: systemd: invalid PACKAGECONFIG: curl [invalid-packageconfig]

Support for curl is currently enabled through journal-upload:

    PACKAGECONFIG[journal-upload] = "-Dlibcurl=true,-Dlibcurl=false,curl"

While it might be more appropriate to deprecate "journal-upload"
in favor of a "curl" PACKAGECONFIG entry, simply fix the importd
comment for now by stating upload-journal instead of curl.

Signed-off-by: Vivien Didelot <vdidelot@pbsc.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>