[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/conf.py b/conf.py
index 9e5de12..de2dd26 100644
--- a/conf.py
+++ b/conf.py
@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 # -----------------------------------------------------------------------
-# Copyright 2019-2024 Open Networking Foundation Contributors
+# Copyright 2019-2026 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.
@@ -14,7 +14,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 # -----------------------------------------------------------------------
-# SPDX-FileCopyrightText: 2019-2024 Open Networking Foundation Contributors
+# SPDX-FileCopyrightText: 2019-2026 Linux Foundation Broadband Contributors
 # SPDX-License-Identifier: Apache-2.0
 # -----------------------------------------------------------------------
 # Intent:
@@ -60,7 +60,7 @@
 
 project = "VOLTHA Docs"
 copyright = (
-    "Copyright 2019-2025 Open Networking Foundation Contributors"
+    "Copyright 2019-2025 Linux Foundation Broadband Contributors"
 )
 author = "VOLTHA Contributors"