An https:// OTLP gRPC endpoint gets the "sending telemetry unencrypted" warning #333

OpenTelemetryConfig.__post_init__ warns "OTLP exporter sending telemetry unencrypted to non-local host ..." for every gRPC endpoint that _parse_remote_insecure_host (lite_bootstrap/instruments/opentelemetry_instrument.py:103-120) reports. That method returns the host whenever opentelemetry_insecure is truthy (default True) and the host is not local, whatever the scheme. The gRPC exporter, though, forces TLS for an https scheme even when insecure=True is passed (opentelemetry/exporter/otlp/proto/grpc/exporter.py:316-317 in 1.44; the 1.28 floor does the same at :208-218). So OpenTelemetryConfig(opentelemetry_endpoint="https://collector.example.com:4317") warns while the exporter's _insecure is False. Reproduced on 705d8a3 while checking #322.

The warning is wrong on the safe side: telemetry is encrypted, and the user is told to change a setting that has no effect.

Work

• Test first: OpenTelemetryConfig(opentelemetry_endpoint="https://collector.example.com:4317") with the default opentelemetry_insecure emits no warning (warnings.simplefilter("error"), next to test_opentelemetry_config_no_warning_for_local_endpoints in tests/instruments/test_opentelemetry_instrument.py). It fails today.
• In _parse_remote_insecure_host, return None when the parsed scheme is https. urlparse lowercases the scheme, so HTTPS:// is covered.
• Keep test_opentelemetry_config_warns_for_remote_endpoints (:234-247) as it is: schemeless, http:// and grpc:// endpoints still warn.

Verify: the new test and the existing insecure-warning tests pass.

Not breaking: one false-positive warning goes away. #322 later changes how the effective value is resolved; this fix stands either way.