docs: Improve documentation for the toTitleCase function (no-changelog) (#8140)

## Summary
Update description of `toTitleCase` to better explain what it does.


## Related tickets and issues

https://linear.app/n8n/issue/PAY-857/expressions-totitlecase-fails-to-lowercase-the-non-leading-letters


## Review / Merge checklist
- [ ] PR title and summary are descriptive. **Remember, the title
automatically goes into the changelog. Use `(no-changelog)` otherwise.**
([conventions](https://github.com/n8n-io/n8n/blob/master/.github/pull_request_title_conventions.md))
- [ ] [Docs updated](https://github.com/n8n-io/n8n-docs) or follow-up
ticket created.
- [ ] Tests included.

---------

Co-authored-by: Iván Ovejero <ivov.src@gmail.com>

packages/workflow/src/Extensions/StringExtensions.ts

@@ -418,7 +418,8 @@ toSnakeCase.doc = {
 
 toTitleCase.doc = {
 	name: 'toTitleCase',
-	description: 'Formats a string to title case. Example: "This Is a Title".',
+	description:
+		'Formats a string to title case. Example: "This Is a Title". Will not change already uppercase letters to prevent losing information from acronyms and trademarks such as iPhone or FAANG.',
 	returnType: 'string',
 	docURL:
 		'https://docs.n8n.io/code/builtin/data-transformation-functions/strings/#string-toTitleCase',