backport-create-issue: flush line before overprinting

backport-create-issue: flush line before overprinting

When iterating over "Pending Backport" issues, the script displays
a message for each issue, like so:

    Examining issue#53432 (345/543)

Since a newline is not printed, each subsequent message overwrites
the previous one. But the last one remained on the screen and was
being overwritten by a shorter log message, leaving behind an
unwanted artifact:

    INFO:root:Processed 334 issues)

Fixes: 8495d37695d43ea38e1b70851e4a6127ebb4fc76
Signed-off-by: Nathan Cutler <ncutler@suse.com>