Exclude out/binaries/gitlab-runner-helper from binaries artifacts

What does this MR do?

It leverages the new artifacts:exclude keyword to fix the issue introduced in !2114 (merged), where helper binaries were inadvertently captured in the artifacts.

Why was this MR needed?

See #26560 (closed)

The change in the target location for the helper binaries introduced in !2114 (merged) caused the helper binaries to inadvertently be captured in the artifacts for the .binaries-derived jobs.

What's the best way to test this MR?

Check the logs of binaries jobs, the state should match the following:

job	artifacts
binaries windows/386 windows/amd64	2 matching files
binaries linux/386 linux/amd64 linux/arm linux/arm64	5 matching files

What are the relevant issue numbers?

Closes #26560 (closed)