test(otel): un-gate nodejs for postgres DB OTel semantics

dd-trace-js#8961 (stacked on the HTTP semantics PR) implements DB OTel
semantic conventions, so Test_PostgresOtelSemantics now passes for nodejs.
Drop the missing_feature gate.

Verified by replay against the tracer build: OTEL_SEMANTICS_DB 9 passed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: khanayan123

manifests/nodejs.yml

@@ -1972,7 +1972,6 @@ manifest:
         express5: *ref_5_90_0
         fastify: *ref_5_90_0
   tests/integrations/test_mongo.py::Test_Mongo: missing_feature (Endpoint is not implemented on weblog)
-  tests/integrations/test_otel_db_semantics.py::Test_PostgresOtelSemantics: missing_feature (DB OTel semantics not implemented; DD_TRACE_OTEL_SEMANTICS_ENABLED covers HTTP only)
   tests/integrations/test_otel_drop_in.py::Test_Otel_Drop_In: missing_feature
   tests/integrations/test_service_overrides.py::Test_SqlServiceNameSource: irrelevant (Only implemented for Java)
   tests/integrations/test_sql.py::Test_Sql: missing_feature (Endpoint is not implemented on weblog)