small changes 2

Author: katiagatt

book/syntax_exercises/013.md

@@ -45,14 +45,6 @@ bibliography: references.bib
 :class: note
 
 A front matter header is a block of configuration settings written in YAML and placed at the very top of a Markdown file, enclosed between triple dashes `---`. It allows you to specify page-level options such as the title, tags, or the bibliography file to use.
-
-For example, the following tells Jupyter Book to use `references.bib` for any citations on that page:
-
-```yaml
----
-bibliography: references.bib
----
-```
 ````