go.mod: bump ebpf, go-git, go-billy and aws-sdk-go-v2 for govulncheck (#20920)

Bump five dependencies to resolve the following advisories;
GO-2026-6238, GO-2026-5764, GO-2026-5597, GO-2026-5490, GO-2026-5496,
GO-2026-5105.

Updates tailscale/corp#9497

Signed-off-by: Tom Proctor <tomhjp@users.noreply.github.com>