fix: javadoc error

Author: pmbittner

src/main/java/org/variantsync/diffdetective/metadata/Metadata.java

@@ -71,7 +71,7 @@ static <T> T mergeEqual(T a, T b) {
     /**
      * Same as {@link #mergeEqual(Object, Object)} but does not crash when the two values are unequal.
      * Instead, both values are merged using the supplied function.
-     * The supplied function is called only if the two given values are unequal (according to {@link Object::equals}).
+     * The supplied function is called only if the two given values are unequal (according to {@link Object#equals(Object)}).
      *
      * <p>The value {@code null} is treated as the neutral element in the sense that no exception is
      * thrown if an element is {@code null}. In this case return value is defined by {@code