Update pulpcon last editions links and stats

[pedro-psb]

This PR does:

• Updates the info about last editions of PulpCon with proper links, dates and stats.
• Change date format (the world doesnt have a consensus if it should be mm/dd or dd/mm)

Got the pulpcore dates with:

git tag -l "3.*.0" | sort -V | while read tag; do
    if [ -n "$tag" ]; then
        # Get short SHA and commit date for the tag
        short_sha=$(git rev-parse --short "$tag")
        commit_date=$(git log -1 --format="%cd" --date=short "$tag")

        printf "%-12s %s %s\n" "$tag" "$short_sha" "$commit_date"
    fi
done