Release process: fix puppet-tails remote computation

refs: #17744

And in passing, fix typo in non-capturing regexp specifier: ":?" → "?:".

wiki/src/contribute/release_process.mdwn

@@ -946,7 +946,7 @@ before starting the wrapper from `puppet-tails`:
        set -eu
        WORK_DIR=$(mktemp -d)
        TAILS_REMOTE="$(git -C "${RELEASE_CHECKOUT?:}" remote get-url origin)"
-       PUPPET_TAILS_REMOTE=$(echo -n "${TAILS_REMOTE?:}" | perl -p -E 's,:tails(:?[.]git)?\z,:puppet-tails,')
+       PUPPET_TAILS_REMOTE=$(echo -n "${TAILS_REMOTE?:}" | perl -p -E 's,:tails/tails(?:[.]git)?\z,:tails/puppet-tails,')
        cd "${WORK_DIR?:}"
        git clone "$PUPPET_TAILS_REMOTE"
        sudo -l