Revert "markdown: Add support for inline HTML img tags inside text (zed-industries#37264)" (zed-industries#37893)

This reverts commit e1a5d29.

This have regressed Zed release notes' wrapping which we do not want to
do on a release day:
zed-industries#37264 (comment)

Release Notes:

- N/A

Author: SomeoneToIgnore

crates/markdown_preview/src/markdown_elements.rs

@@ -155,7 +155,7 @@ pub struct ParsedMarkdownText {
     /// Where the text is located in the source Markdown document.
     pub source_range: Range<usize>,
     /// The text content stripped of any formatting symbols.
-    pub contents: SharedString,
+    pub contents: String,
     /// The list of highlights contained in the Markdown document.
     pub highlights: Vec<(Range<usize>, MarkdownHighlight)>,
     /// The regions of the various ranges in the Markdown document.