drop CI testing of Node.js v23; that can be handled separately (see open-telemetry/opentelemetry-js#5416 and open-telemetry/opentelemetry-js#5415)

Author: trentm

.github/workflows/unit-test.yml

@@ -43,7 +43,6 @@ jobs:
           - "20.6.0"
           - "20"
           - "22"
-          - "23"
         include:
             - node: 18
               code-coverage: true