Remove unnecessary warning

With the introduction of standard creation infos in SPDX 3.0.1, we will
be copying the same URIs to different model stores.  This removes the
warning when this occurs.

src/main/java/org/spdx/library/ModelCopyManager.java

@@ -448,7 +448,10 @@ private String sourceUriToObjectUri(String sourceUri, IdType idType, IModelStore
 		}
 		if (Objects.isNull(toNamespace) || toNamespace.isEmpty() || 
 				sourceUri.startsWith(toNamespace)) {
-            logger.warn("{} already exists - possibly overwriting properties due to a copy from a different model store.", sourceUri);
+			if (!sourceUri.startsWith("https://spdx.org")) {
+				// It is not a pre-defined SPDX URI
+				logger.warn("{} already exists - possibly overwriting properties due to a copy from a different model store.", sourceUri);
+			}
 			return sourceUri;
 		}
 		switch (idType) {