rename api file to client

Author: keith-decker

…enai/src/opentelemetry/util/genai/api.py …i/src/opentelemetry/util/genai/client.pyutil/opentelemetry-util-genai/src/opentelemetry/util/genai/api.py renamed to util/opentelemetry-util-genai/src/opentelemetry/util/genai/client.py util/opentelemetry-util-genai/src/opentelemetry/util/genai/api.py renamed to util/opentelemetry-util-genai/src/opentelemetry/util/genai/client.py

@@ -8,7 +8,7 @@
 from opentelemetry.sdk.trace.export.in_memory_span_exporter import (
     InMemorySpanExporter,
 )
-from opentelemetry.util.genai.api import (
+from opentelemetry.util.genai.client import (
     llm_start,
     llm_stop,
 )