Update OpenTelemetry dependencies to latest versions

Core packages (opentelemetry-go):
- go.opentelemetry.io/otel: v1.38.0 → v1.39.0
- go.opentelemetry.io/otel/metric: v1.38.0 → v1.39.0
- go.opentelemetry.io/otel/trace: v1.38.0 → v1.39.0
- go.opentelemetry.io/otel/sdk: v1.38.0 → v1.39.0

Exporters:
- go.opentelemetry.io/otel/exporters/otlp/otlptrace: v1.34.0 → v1.39.0
- go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc: v1.34.0 → v1.39.0

Contrib instrumentation (opentelemetry-go-contrib):
- go.opentelemetry.io/contrib/.../otelhttp: v0.61.0 → v0.64.0
- go.opentelemetry.io/contrib/.../otelrestful: v0.44.0 → v0.64.0

Protocol definitions (opentelemetry-proto-go):
- go.opentelemetry.io/proto/otlp: v1.5.0 → v1.9.0

Notable changes:
- Go 1.24 is now the minimum required version (Go 1.23 support dropped) for OTEL components
- Performance: ~4x improvement in histogram concurrent operations; xxhash
  replaces fnv for attribute hashing
- Fixed goroutine leak in span processors when context is canceled
- otelrestful migrated semantic conventions from v1.20.0 to v1.34.0
  (e.g., http.method → http.request.method)
- Partial OTLP export errors now surfaced instead of being silently dropped
- otelrestful no longer depends on json-iterator/go, modern-go/concurrent,
  or modern-go/reflect2; unwanted-dependencies.json updated accordingly

Signed-off-by: Davanum Srinivas <davanum@gmail.com>

Kubernetes-commit: c40ea60b9f193fbead586f9fd6cc26f7b77312ff