Merge #19201: ci: Switch to bitcoincore.org download

fa4cd1fdae ci: Switch to bitcoincore.org download (MarcoFalke)

Pull request description:

  bitcoin.org is down and not in our control, so it seems odd to rely on it for our ci infrastructure

ACKs for top commit:
  troygiorshev:
    ACK fa4cd1f

Tree-SHA512: f9f0e9c69a52b8b1906ceae195e8bcc189799fb39be921b26e3a37d1f8f3999831f86c96c3546848c0d01429c36cfb2d7c5f314655ac5282d3e8e4cdd838960e

contrib/devtools/previous_release.sh

@@ -137,7 +137,7 @@ pushd "$TARGET" || exit 1
         else
             BIN_PATH="bin/bitcoin-core-${tag:1}"
         fi
-        URL="https://bitcoin.org/$BIN_PATH/bitcoin-${tag:1}-$PLATFORM.tar.gz"
+        URL="https://bitcoincore.org/$BIN_PATH/bitcoin-${tag:1}-$PLATFORM.tar.gz"
         echo "Fetching: $URL"
         if ! curl -O -f $URL; then
             echo "Download failed."