Log deprecation warning when creating SignalFxMeterRegistry (micrometer-metrics#5824)

Signed-off-by: jason plumb <[email protected]>

Author: breedx-splk

implementations/micrometer-registry-signalfx/src/main/java/io/micrometer/signalfx/SignalFxMeterRegistry.java

@@ -80,6 +80,7 @@ public SignalFxMeterRegistry(SignalFxConfig config, Clock clock) {
 
     public SignalFxMeterRegistry(SignalFxConfig config, Clock clock, ThreadFactory threadFactory) {
         super(config, clock);
+        logger.warn("SignalFxMeterRegistry is deprecated in favor of micrometer-registry-otlp.");
         this.config = config;
 
         URI apiUri = URI.create(config.uri());