Drop brackets from generated changelog heading (#1039)

The release script in scripts/publish.sh extracts the changelog block
with the awk pattern `^### <version>( |$|-)`, which does not match
`### [<version>]`. Generate the heading as `### VERSION - DATE` so
publish.sh can find it.

Author: donnchawp

scripts/pre-build.sh

@@ -81,7 +81,7 @@ else
 fi
 TODAY="$(date +%Y-%m-%d)"
 {
-	echo "### [$VERSION] - $TODAY"
+	echo "### $VERSION - $TODAY"
 	gh pr list \
 		--state merged \
 		--base trunk \