Use packages.matrix.org for packages (#5067)

* Use packages.matrix.org for packages

See https://github.com/vector-im/riot-web/issues/9497 (applies to more than just Olm)

* changelog

INSTALL.md

@@ -257,13 +257,13 @@ https://github.com/spantaleev/matrix-docker-ansible-deploy
 #### Matrix.org packages
 
 Matrix.org provides Debian/Ubuntu packages of the latest stable version of
-Synapse via https://matrix.org/packages/debian/. To use them:
+Synapse via https://packages.matrix.org/debian/. To use them:
 
 ```
 sudo apt install -y lsb-release curl apt-transport-https
-echo "deb https://matrix.org/packages/debian `lsb_release -cs` main" |
+echo "deb https://packages.matrix.org/debian `lsb_release -cs` main" |
     sudo tee /etc/apt/sources.list.d/matrix-org.list
-curl "https://matrix.org/packages/debian/repo-key.asc" |
+curl "https://packages.matrix.org/debian/repo-key.asc" |
     sudo apt-key add -
 sudo apt update
 sudo apt install matrix-synapse-py3

changelog.d/5067.misc

@@ -0,0 +1 @@
+Update documentation for where to get Synapse packages.