Add "experimental" in configuration key

Co-authored-by: Brian Marks <[email protected]>

Author: cecile75

dd-trace-api/src/main/java/datadog/trace/api/config/TracerConfig.java

@@ -74,7 +74,7 @@ public final class TracerConfig {
 
   public static final String SPLIT_BY_TAGS = "trace.split-by-tags";
   // trace latency interceptor value should be in ms
-  public static final String TRACE_KEEP_LATENCY_THRESHOLD_MS = "trace.keep.latency.threshold.ms";
+  public static final String TRACE_KEEP_LATENCY_THRESHOLD_MS = "trace.experimental.keep.latency.threshold.ms";
   public static final String SCOPE_DEPTH_LIMIT = "trace.scope.depth.limit";
   public static final String SCOPE_STRICT_MODE = "trace.scope.strict.mode";
   public static final String SCOPE_ITERATION_KEEP_ALIVE = "trace.scope.iteration.keep.alive";