Cleanup leftover feature flag (#2458)

Author: cijothomas

opentelemetry-sdk/CHANGELOG.md

@@ -92,7 +92,10 @@
       `experimental_metrics_periodicreader_with_async_runtime`.  
     - Continue enabling one of the async runtime feature flags: `rt-tokio`,
       `rt-tokio-current-thread`, or `rt-async-std`.
-      
+
+    Feature flag "experimental_metrics_periodic_reader_no_runtime" is removed as the PeriodicReader
+    offered under that feature flag is now the default.
+
   - Bump msrv to 1.75.0.
 
 - *Breaking* : [#2314](https://github.com/open-telemetry/opentelemetry-rust/pull/2314)

opentelemetry-sdk/Cargo.toml

@@ -53,7 +53,6 @@ rt-tokio = ["tokio", "tokio-stream"]
 rt-tokio-current-thread = ["tokio", "tokio-stream"]
 rt-async-std = ["async-std"]
 internal-logs = ["tracing"]
-experimental_metrics_periodic_reader_no_runtime = ["metrics"]
 experimental_metrics_periodicreader_with_async_runtime = ["metrics"]
 spec_unstable_metrics_views = ["metrics"]
 experimental_logs_batch_log_processor_with_async_runtime = ["logs"]