Exporter/Jaeger: Fix an annotation. (census-instrumentation#1571)

Author: songy23

exporters/trace/jaeger/src/main/java/io/opencensus/exporter/trace/jaeger/JaegerExporterHandler.java

@@ -365,7 +365,8 @@ private static Tag descriptionToTag(final String description) {
     return tag;
   }
 
-  private static @Nullable Tag spanKindToTag(@Nullable final io.opencensus.trace.Span.Kind kind) {
+  @Nullable
+  private static Tag spanKindToTag(@Nullable final io.opencensus.trace.Span.Kind kind) {
     if (kind == null) {
       return null;
     }