Backport #40118 by @lazerg
The approver limit was checked before writing each `Reviewed-by:` line
but compared with `>`, so the default merge message got one more trailer
than `DEFAULT_MERGE_MESSAGE_MAX_APPROVERS` allows (2 with a limit of 1,
11 with the default 10). It now stops once the limit is reached.
Fixes https://github.com/go-gitea/gitea/issues/40116
Assisted-by: Claude Code:claude-opus-5-5
Co-authored-by: Lazizbek Ergashev <lazerg2@gmail.com>