Remove non-default feature from doc test (#2346)

Author: bantonsson

opentelemetry-semantic-conventions/scripts/templates/registry/rust/metric.rs.j2

@@ -26,7 +26,7 @@
 //!     .u64_histogram(semconv::metric::HTTP_SERVER_REQUEST_DURATION)
 //!     .with_unit("By")
 //!     .with_description("Duration of HTTP server requests.")
-//!     .init();
+//!     .build();
 //! ```
 
 {% for root_ns in ctx %}

opentelemetry-semantic-conventions/scripts/templates/registry/rust/resource.rs.j2

@@ -22,7 +22,6 @@
 //! let _tracer = TracerProvider::builder()
 //!     .with_config(config().with_resource(Resource::new(vec![
 //!         KeyValue::new(semconv::resource::SERVICE_NAME, "my-service"),
-//!         KeyValue::new(semconv::resource::SERVICE_NAMESPACE, "my-namespace"),
 //!     ])))
 //!     .build();
 //! ```

opentelemetry-semantic-conventions/src/resource.rs

@@ -21,7 +21,6 @@
 //! let _tracer = TracerProvider::builder()
 //!     .with_config(config().with_resource(Resource::new(vec![
 //!         KeyValue::new(semconv::resource::SERVICE_NAME, "my-service"),
-//!         KeyValue::new(semconv::resource::SERVICE_NAMESPACE, "my-namespace"),
 //!     ])))
 //!     .build();
 //! ```