Rephrase to use "Constant" instead of "Value"

When referring to the instances of JsonInclude.Value, to avoid too much
overloading with "values" referring to values being serialized to JSON.

See also discussion:
#314 (comment)

Author: runeflobakk

src/main/java/com/fasterxml/jackson/annotation/JsonInclude.java

@@ -269,35 +269,35 @@ public static class Value
         private static final long serialVersionUID = 1L;
 
         /**
-         * Value that indicates that property is to be always included,
+         * Constant that indicates that property is to be always included,
          * independent of value of the property.
          * <p>
          * This will specify the same setting for including a value both
          * on <b>Java object level</b> as well as when <b>contained</b>
          * in an object reference (see {@link JsonInclude} for further
-         * details on this distinction)
+         * details on this distinction).
          *
          * @since 2.21
          */
         public final static Value ALL_ALWAYS = Value
                 .construct(Include.ALWAYS, Include.ALWAYS);
 
         /**
-         * Value that indicates that only properties with non-null
+         * Constant that indicates that only properties with non-null
          * values are to be included.
          * <p>
          * This will specify the same setting for including a value both
          * on <b>Java object level</b> as well as when <b>contained</b>
          * in an object reference (see {@link JsonInclude} for further
-         * details on this distinction)
+         * details on this distinction).
          *
          * @since 2.21
          */
         public final static Value ALL_NON_NULL = Value
                 .construct(Include.NON_NULL, Include.NON_NULL);
 
         /**
-         * Value that indicates that properties are included unless their value
+         * Constant that indicates that properties are included unless their value
          * is:
          * <ul>
          *  <li>null</li>
@@ -310,22 +310,22 @@ public static class Value
          * This will specify the same setting for including a value both
          * on <b>Java object level</b> as well as when <b>contained</b>
          * in an object reference (see {@link JsonInclude} for further
-         * details on this distinction)
+         * details on this distinction).
          *
          * @since 2.21
          */
         public final static Value ALL_NON_ABSENT = Value
                 .construct(Include.NON_ABSENT, Include.NON_ABSENT);
 
         /**
-         * Value that indicates that only properties with null value,
+         * Constant that indicates that only properties with null value,
          * or what is considered empty, are not to be included.
          * See {@link Include#NON_EMPTY} for further details.
          * <p>
          * This will specify the same setting for including a value both
          * on <b>Java object level</b> as well as when <b>contained</b>
          * in an object reference (see {@link JsonInclude} for further
-         * details on this distinction)
+         * details on this distinction).
          *
          * @since 2.21
          */
@@ -339,7 +339,7 @@ public static class Value
          * This will specify the same setting for including a value both
          * on <b>Java object level</b> as well as when <b>contained</b>
          * in an object reference (see {@link JsonInclude} for further
-         * details on this distinction)
+         * details on this distinction).
          *
          * @since 2.21
          */