CASSANDRASC-54 Add NOTICE.txt file

The NOTICE.txt file is currently missing in the repository. This commit adds the file to
comply with ASF's guidance.

patch byFrancisco Guerrero; reviewed by Dinesh Joshi, Michael Semb Wever for CASSANDRASC-54
diff --git a/LICENSE.txt b/LICENSE.txt
index d5c4984..d645695 100644
--- a/LICENSE.txt
+++ b/LICENSE.txt
@@ -200,10 +200,3 @@
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
-
-
-THIRD-PARTY DEPENDENCIES
-========================
-Convenience copies of some third-party dependencies are distributed with
-Apache Cassandra as Java jar files in lib/. Licensing information for
-these files can be found in the lib/licenses directory.
diff --git a/NOTICE.txt b/NOTICE.txt
new file mode 100644
index 0000000..aa9b8cc
--- /dev/null
+++ b/NOTICE.txt
@@ -0,0 +1,6 @@
+Apache Cassandra Sidecar
+Copyright 2023- The Apache Software Foundation
+
+This product includes software developed by The Apache Software
+Foundation (http://www.apache.org/).
+