[chore] Explicitly note that service and otelcol are not part of 1.0 (#10643)

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#### Description

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Explicitly excludes service and otelcol from 1.0 efforts.

These modules are useful for distribution maintainers but not end-users,
for which the 1.0 effort is targeted.

Author: mx-psi

docs/ga-roadmap.md

@@ -38,6 +38,7 @@ Additionally, when considering bug reports we will prioritize:
 Explicitly, the following are not in the scope of v1 for the purposes of this document:
 
 * stabilization of additional components/APIs needed by distribution maintainers. Vendors are not the audience
+  * This explicitly excludes the `service` and `otelcol` modules, for which we will only guarantee that there are no breaking changes impacting end-users of the binary after 1.0, while Go API only changes will continue to be admissible until these modules are tagged as 1.0.
 * Collector Builder
 * telemetrygen
 * mdatagen