Update creating-diagrams.md

Fix a couple typos

content/get-started/writing-on-github/working-with-advanced-formatting/creating-diagrams.md

@@ -8,7 +8,7 @@ shortTitle: Create diagrams
 
 ## About creating diagrams
 
-You can create diagrams in Markdown using three different syntaxes: mermaid, geoJSON and topoJSON, and ASCII STL. Diagram rendering is available in {% data variables.product.prodname_github_issues %}, {% data variables.product.prodname_discussions %}, pull requests, wikis, and Markdown files.
+You can create diagrams in Markdown using four different syntaxes: mermaid, geoJSON, topoJSON, and ASCII STL. Diagram rendering is available in {% data variables.product.prodname_github_issues %}, {% data variables.product.prodname_discussions %}, pull requests, wikis, and Markdown files.
 
 ## Creating Mermaid diagrams