bin/get-pick-list.sh: sha1 commits can be smaller than 8 chars
The script only handles commits with "Fixes: sha1" where sha1 is
equal or great than 8 chars. But sha1 can be smaller, like 7 chars.
This commit relax the restriction to handle sha1 4 or more chars.
Fixes 533fead4 ("bin/get-pick-list.sh: tweak the commit sha matching pattern")
Signed-off-by: Juan A. Suarez Romero jasuarez@igalia.com