[VOL-5545] Update voltha docs

- release notes for VOLTHA versions 2.6 to 2.15 with new Jira links and adjust release schedule details
- update old links
- remove ONF references and links
- update e-mail links
- update copright notices

Change-Id: Id6be18986a8f52f2dfcc07e2b0d2efcb0ae1c0e4
Signed-off-by: serkant.uluderya <serkant.uluderya@netsia.com>
diff --git a/overview/contributing/copyright/golang.rst b/overview/contributing/copyright/golang.rst
index 13ec153..2c0e045 100644
--- a/overview/contributing/copyright/golang.rst
+++ b/overview/contributing/copyright/golang.rst
@@ -5,7 +5,7 @@
    :caption: Copyright Syntax
 
    /* -----------------------------------------------------------------------
-    * Copyright 2017-2024 Open Networking Foundation Contributors
+    * Copyright 2017-2026 Linux Foundation Broadband Contributors
     *
     * Licensed under the Apache License, Version 2.0 (the "License");
     * you may not use this file except in compliance with the License.
@@ -19,7 +19,7 @@
     * See the License for the specific language governing permissions and
     * limitations under the License.
     * -----------------------------------------------------------------------
-    * SPDX-FileCopyrightText: 2017-2024 Open Networking Foundation Contributors
+    * SPDX-FileCopyrightText: 2017-2026 Linux Foundation Broadband Contributors
     * SPDX-License-Identifier: Apache-2.0
     * -----------------------------------------------------------------------
     */