Recent change to Towncrier generation doesn't handle newlines properly

[webknjaz]

@uranusjr I overlooked one thing — it appears that your change adding breaks the title now: https://pip--9805.org.readthedocs.build/en/9805/news/#changelog

Originally posted by @webknjaz in #9805 (comment)

[webknjaz]

@uranusjr ☝️ just documenting this for now but the fix should be trivial — s/-}}/}}/ on the first line of the towncrier template.