Deprecate the OT Trace propagator

[carlosalberto]

Similarly to #4786, we should deprecate the OT Trace propagator as:

1. The OT Trace propagator format was used by some OpenTracing clients/instrumentation long before the W3C trace format appeared.
2. Doing this would signal that any existing clients/deployments need to start using the better, more complete W3C trace context format instead.

It has been years since OpenTracing has been sunset, so this shouldn't be a problem IMHO.

cc @tedsuo

[mx-psi]

@open-telemetry/technical-committee Please take a look!

[jack-berg]

Discussed in 1/21/26 TC meeting and we have no issues about this. Adjusted to triage:accepted:needs-sponsor. @carlosalberto do you have interest in sponsoring / driving this?