Issue #559: Fixed unexpected text in Javadoc.

Signed-off-by: Juergen Fickel <juergen.fickel@bosch.io>

base/model/src/main/java/org/eclipse/ditto/base/model/headers/DittoHeadersBuilder.java

@@ -98,14 +98,14 @@ default B randomCorrelationId() {
 
     /**
      * Sets the specified String as channel of the Signal/Exception.
-     * Allowed values are {@value "twin"} and {@value "live"}.
-     * If omitted, {@value "twin"} is used as default.
+     * Allowed values are {@code "twin"} and {@code "live"}.
+     * If omitted, {@code "twin"} is used as default.
      *
      * @param channel the channel of the Signal/Exception to be set.
      * {@code null} removes an already set channel header.
      * @return this builder for Method Chaining.
      * @throws org.eclipse.ditto.base.model.exceptions.DittoHeaderInvalidException if {@code channel} after trimming and
-     * converting to lower case does not match {@value "twin"} or {@value "live"}.
+     * converting to lower case does not match {@code "twin"} or {@code "live"}.
      */
     B channel(@Nullable CharSequence channel);