Update CODEOWNERS to reflect spec sponsor role (#4170)

Followup to open-telemetry/community#2070

Should be merged in lockstep with
open-telemetry/opentelemetry-proto#572

Upon merging, I will:
- Rename
[spec-approvers](https://github.com/orgs/open-telemetry/teams/specs-approvers)
to `spec-sponsors`
- Add all [current
sponsors](https://github.com/open-telemetry/community/blob/main/community-members.md#specifications-and-proto)
to `spec-sponsors`
- Delete
[spec-metrics-approvers](https://github.com/orgs/open-telemetry/teams/specs-metrics-approvers),
[spec-trace-approvers](https://github.com/orgs/open-telemetry/teams/specs-trace-approvers),
[spec-logs-approvers](https://github.com/orgs/open-telemetry/teams/specs-logs-approvers)

Note, there are still references to spec approvers in
[CONTRIBUTING.md](https://github.com/open-telemetry/opentelemetry-specification/blob/main/CONTRIBUTING.md).
As discussed in #3821 there are a variety of issues with the spec issue
management process, including consistency. I'm not trying to solve all
of them in this PR - rather, I want to make incremental progress and
reflect a decision that was already made about the spec sponsor role.

---------

Co-authored-by: Trask Stalnaker <trask.stalnaker@gmail.com>
Co-authored-by: Robert Pająk <pellared@hotmail.com>
Co-authored-by: Cijo Thomas <cijo.thomas@gmail.com>

.github/CODEOWNERS

@@ -13,22 +13,4 @@
 #
 
 # Global owners, will be the owners for everything in the repo. Membership is tracked via https://github.com/open-telemetry/community/blob/main/community-members.md 
-*   @open-telemetry/technical-committee @open-telemetry/specs-approvers
-
-# Trace owners (global + trace)
-development/trace/     @open-telemetry/technical-committee @open-telemetry/specs-approvers @open-telemetry/specs-trace-approvers
-specification/trace/    @open-telemetry/technical-committee @open-telemetry/specs-approvers @open-telemetry/specs-trace-approvers
-
-# Metrics owners (global + metrics)
-development/metrics/   @open-telemetry/technical-committee @open-telemetry/specs-approvers @open-telemetry/specs-metrics-approvers
-specification/metrics/  @open-telemetry/technical-committee @open-telemetry/specs-approvers @open-telemetry/specs-metrics-approvers
-
-# Logs owners (global + logs)
-development/logs/      @open-telemetry/technical-committee @open-telemetry/specs-approvers @open-telemetry/specs-logs-approvers
-specification/logs/     @open-telemetry/technical-committee @open-telemetry/specs-approvers @open-telemetry/specs-logs-approvers
-
-# Semantic Conventions owners (global)
-specification/semantic-conventions.md @open-telemetry/technical-committee @open-telemetry/specs-approvers @open-telemetry/specs-semconv-approvers
-specification/telemetry-stability.md @open-telemetry/technical-committee @open-telemetry/specs-approvers @open-telemetry/specs-semconv-approvers
-# Note: Common is about naming conventions, relevant to semconv
-specification/common/ @open-telemetry/technical-committee @open-telemetry/specs-approvers @open-telemetry/specs-semconv-approvers
+*   @open-telemetry/technical-committee @open-telemetry/spec-sponsors