doc: fix last missing © symbols

 CODE_OF_CONDUCT.md | 2 +-
 CONTRIBUTING.md    | 2 +-
 PACKAGING.md       | 2 +-
 README.md          | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/CODE_OF_CONDUCT.md b/CODE_OF_CONDUCT.md
index 71798e7..6e9dd03 100644
--- a/CODE_OF_CONDUCT.md
+++ b/CODE_OF_CONDUCT.md
@@ -1,5 +1,5 @@
 <!--
-SPDX-FileCopyrightText: 2024 The River Developers
+SPDX-FileCopyrightText: © 2024 The River Developers
 SPDX-License-Identifier: CC-BY-SA-4.0
 -->
 # River Code of Conduct
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index c6e31e4..641d81b 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -1,5 +1,5 @@
 <!--
-SPDX-FileCopyrightText: 2020 The River Developers
+SPDX-FileCopyrightText: © 2020 The River Developers
 SPDX-License-Identifier: CC-BY-SA-4.0
 -->
 
diff --git a/PACKAGING.md b/PACKAGING.md
index c562bf9..2f33dad 100644
--- a/PACKAGING.md
+++ b/PACKAGING.md
@@ -1,5 +1,5 @@
 <!--
-SPDX-FileCopyrightText: 2022 The River Developers
+SPDX-FileCopyrightText: © 2022 The River Developers
 SPDX-License-Identifier: CC-BY-SA-4.0
 -->
 
diff --git a/README.md b/README.md
index 9361f42..5b5e874 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,5 @@
 <!--
-SPDX-FileCopyrightText: 2020 The River Developers
+SPDX-FileCopyrightText: © 2020 The River Developers
 SPDX-License-Identifier: CC-BY-SA-4.0
 -->