markdown: Make cx the last parameter to Markdown::new_text (#21497)

This PR is a follow-up to
https://github.com/zed-industries/zed/pull/21487 to make sure that the
`cx` is the last parameter to `Markdown::new_text` as well.

Release Notes:

- N/A

crates/markdown/src/markdown.rs

@@ -97,8 +97,8 @@ impl Markdown {
         source: String,
         style: MarkdownStyle,
         language_registry: Option<Arc<LanguageRegistry>>,
-        cx: &ViewContext<Self>,
         fallback_code_block_language: Option<String>,
+        cx: &ViewContext<Self>,
     ) -> Self {
         let focus_handle = cx.focus_handle();
         let mut this = Self {