Update 1.6 source files to comply with the new checkstyle rule

implementations/micrometer-registry-health/src/main/java/io/micrometer/health/ServiceLevelObjective.java

@@ -334,7 +334,7 @@ public final NumericQuery value(Function<Search, Search> search) {
             }
         }
 
-        public static abstract class NumericQuery {
+        public abstract static class NumericQuery {
             protected final String name;
             private final Tags tags;