Make sure auto-generated release notes don't overflow the length limit that shows on GitHub release page

This release:

https://github.com/dolthub/dolt/releases/tag/v0.75.13

overflowed the length that shows on the release page:

https://github.com/dolthub/dolt/releases

Multiple people contacted us looking for a PR number they could not find when searching the releases page.

We need our release notes generator to truncate descriptions down so that we never over-run the allotted space on the releases page.

Start by locating the release notes generator and compare its output with the linked v0.75.13 release and the releases page. Determine the visible length limit, then verify that generated notes stay within it while retaining enough description to find referenced pull requests.

Written by the indexing model from the issue text.