markdown: Remove unused message_inline_ref.

Fixes #32640.
We cannot remove the styles yet since older dropbox previews will still
be using them. We can remove those in a followup issue.

web/styles/rendered_markdown.css

@@ -486,6 +486,9 @@
         margin-bottom: var(--markdown-interelement-space-px);
     }
 
+    /* We used to use this for certain dropbox previews, we are keeping
+       this around as to not break any previous instances of these
+       previews. */
     .message_inline_image_title {
         font-weight: bold;
     }
@@ -640,6 +643,9 @@
         margin-right: 0.75em;
     }
 
+    /* We used to use this for certain dropbox previews, we are keeping
+       this around as to not break any previous instances of these
+       previews. */
     .message_inline_ref {
         margin-bottom: var(--markdown-interelement-space-px);
         margin-inline-start: 5px;

zerver/lib/markdown/__init__.py

@@ -678,14 +678,6 @@ class InlineInterestingLinkProcessor(markdown.treeprocessors.Treeprocessor):
         else:
             img.set("src", image_url)
 
-        if class_attr == "message_inline_ref":
-            summary_div = SubElement(div, "div")
-            title_div = SubElement(summary_div, "div")
-            title_div.set("class", "message_inline_image_title")
-            title_div.text = title
-            desc_div = SubElement(summary_div, "desc")
-            desc_div.set("class", "message_inline_image_desc")
-
     def add_oembed_data(self, root: Element, link: str, extracted_data: UrlOEmbedData) -> None:
         if extracted_data.image is None:
             # Don't add an embed if an image is not found
@@ -1236,7 +1228,6 @@ class InlineInterestingLinkProcessor(markdown.treeprocessors.Treeprocessor):
             uncle = grandparent[insertion_index]
             inline_image_classes = {
                 "message_inline_image",
-                "message_inline_ref",
                 "inline-preview-twitter",
             }
             if (