[REL-4161] switch to printf to allow for backticks in CHANGELOG (#523)

😩 please let this be the last one 😩

Using the heredoc was creating toil because the syntax is kinda fiddly
and `workflow_dispatch` is only available on main, so I needed to create
a PR and get a review for every change. But in the end, using `printf`
is better anyway because it allows for backticks, which bash will try to
run if they appear inside an unquoted heredoc. We'll see if the
CHANGELOG comes out looking okay, but cursor assures me `printf` works
well for multiline content. 🤞
<!-- ld-jira-link -->
---
Related Jira issue: [REL-4161: Migrate ld-find-code-refs from Releaser
to GHA](https://launchdarkly.atlassian.net/browse/REL-4161)
<!-- end-ld-jira-link -->

Author: blaqbern

scripts/release/commit-and-tag.sh

@@ -11,10 +11,7 @@ tag_exists() (
 
 update_changelog() (
   local ts=$(date +"%Y-%m-%d")
-  local changelog_entry=$(cat << EOF
-## [$LD_RELEASE_VERSION] - $ts
-$CHANGELOG_ENTRY
-EOF
+  local changelog_entry=$(printf "## [%s] - %s\n%s\n" "$LD_RELEASE_VERSION" "$ts" "$CHANGELOG_ENTRY")
 
   # insert the new changelog entry (followed by empty line) after line 4
   # of CHANGELOG.md