resize: Rename reset_compose_textarea_max_height.

This no logner just resets the max-height of compose-textarea
but also preview_message_area.

static/js/compose.js

@@ -669,7 +669,7 @@ export function initialize() {
             $("#compose .preview_content"),
             content,
         );
-        resize.reset_compose_textarea_max_height();
+        resize.reset_compose_message_max_height();
     });
 
     $("#compose").on("click", ".undo_markdown_preview", (e) => {