docs: Be explicit about current span in manual instrumentation doc (#1061)
docs: Be explicit about current span in manual instrumentation doc (#1061)

* Be explicit about current span in manual instrumentation doc

* Update website_docs/manual_instrumentation.md

Co-authored-by: Ariel Valentin <b0deeb8a3ad8c82c93a80d7b941ae563874c27a1@users.noreply.github.com>

Co-authored-by: Ariel Valentin <b0deeb8a3ad8c82c93a80d7b941ae563874c27a1@users.noreply.github.com>
Co-authored-by: Francis Bogsanyi <670cd5605830f6b63d443687caab7fc24c3610f8@shopify.com>
open-telemetry/opentelemetry-ruby,open-telemetry/opentelemetry-ruby