Make prefix method in major version public

Signed-off-by: Gary O'Neall <gary@sourceauditor.com>

Author: goneall

src/main/java/org/spdx/core/SpdxCoreConstants.java

@@ -50,7 +50,7 @@ public static SpdxMajorVersion latestVersion() {
 		/**
 		 * @return the string prefix used in all version strings
 		 */
-		String prefix() {
+		public String prefix() {
 			return prefix;
 		}
 	}