fix(proxy): add missing return when Pyroscope profiling is disabled

Without the return, _init_pyroscope would fall through into the try block
and raise ValueError when PYROSCOPE_APP_NAME was not set, even when
LITELLM_ENABLE_PYROSCOPE was false. This caused CI failures on Linux
where pyroscope-io is installed.

litellm/proxy/proxy_server.py

@@ -5831,6 +5831,7 @@ class ProxyStartupEvent:
             verbose_proxy_logger.debug(
                 "LiteLLM: Pyroscope profiling is disabled (set LITELLM_ENABLE_PYROSCOPE=true to enable)."
             )
+            return
         try:
             import pyroscope