fix clang-tidy cppcoreguidelines-avoid-const-or-ref-data-members warning in otlp http

Author: dbarker

exporters/otlp/include/opentelemetry/exporters/otlp/otlp_http_metric_exporter.h

@@ -72,7 +72,7 @@ class OtlpHttpMetricExporter final : public opentelemetry::sdk::metrics::PushMet
   OtlpHttpMetricExporterRuntimeOptions runtime_options_;
 
   // Aggregation Temporality Selector
-  const sdk::metrics::AggregationTemporalitySelector aggregation_temporality_selector_;
+  sdk::metrics::AggregationTemporalitySelector aggregation_temporality_selector_;
 
   // Object that stores the HTTP sessions that have been created
   std::unique_ptr<OtlpHttpClient> http_client_;