Fix inaccurate ServiceInstanceIdResourceProvider class Javadoc

[thswlsqls]

Is your feature request related to a problem? Please describe.
The class Javadoc of ServiceInstanceIdResourceProvider (sdk-extensions/incubator/src/main/java/io/opentelemetry/sdk/extension/incubator/resources/ServiceInstanceIdResourceProvider.java, lines 16-19) is a subjectless sentence fragment that is also factually wrong: it reads "does not implement ResourceProvider, because it depends on all attributes discovered by the other providers." The class implements ConditionalResourceProvider, and ConditionalResourceProvider extends ResourceProvider, so it does implement ResourceProvider transitively.

Describe the solution you'd like
Rewrite the class Javadoc so it is grammatical and correct: state that the provider uses ConditionalResourceProvider rather than a plain ResourceProvider because it must run after the other providers have discovered their attributes. Docs-only; no code, signature, or behavior change.

Describe alternatives you've considered
N/A.

Spec alignment
Not applicable. This is a Javadoc correction, not a behavior or feature change. Scope is orthogonal to #8410 (stabilizing service.instance.id behavior).

Additional context

• Affected module: :sdk-extensions:incubator
• Artifact stability: alpha
• Backward compatible: yes