fix(tracing): use latest version of semconv

All components need to use a consistent `semconv` version or OTel
will emit errors about "cannot merge resource due to conflicting Schema URL".

Switch to the appropriate semconv version, which requires dropping
usage of `httpconv`. Instead, the upstream HTTP client hooks are
used directly. (The lower-level functions are no longer exported by
OTel.)

Signed-off-by: Milas Bowman <milas.bowman@docker.com>

tracing/plugin/otlp.go

@@ -36,7 +36,7 @@ import (
 	"go.opentelemetry.io/otel/propagation"
 	"go.opentelemetry.io/otel/sdk/resource"
 	"go.opentelemetry.io/otel/sdk/trace"
-	semconv "go.opentelemetry.io/otel/semconv/v1.17.0"
+	semconv "go.opentelemetry.io/otel/semconv/v1.21.0"
 )
 
 const exporterPlugin = "otlp"