scripted-diff: Bump copyright headers

-BEGIN VERIFY SCRIPT-
./contrib/devtools/copyright_header.py update ./
-END VERIFY SCRIPT-

contrib/devtools/test_deterministic_coverage.sh

@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 #
-# Copyright (c) 2019 The Bitcoin Core developers
+# Copyright (c) 2019-2020 The Bitcoin Core developers
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 #