Add missing space before 'docker' link in release announcement script (#12612)

changelog.d/12612.bugfix

@@ -0,0 +1 @@
+Fix a typo in the announcement text generated by the Synapse release development script.

scripts-dev/release.py

@@ -434,7 +434,7 @@ def announce() -> None:
         f"""
 Hi everyone. Synapse {current_version} has just been released.
 
-[notes](https://github.com/matrix-org/synapse/releases/tag/{tag_name}) |\
+[notes](https://github.com/matrix-org/synapse/releases/tag/{tag_name}) | \
 [docker](https://hub.docker.com/r/matrixdotorg/synapse/tags?name={tag_name}) | \
 [debs](https://packages.matrix.org/debian/) | \
 [pypi](https://pypi.org/project/matrix-synapse/{current_version}/)"""