Standardize on showConversation function, delete unused functions

ts/state/ducks/composer.ts

@@ -44,6 +44,7 @@ import {
   getLinkPreviewForSend,
   hasLinkPreviewLoaded,
   maybeGrabLinkPreview,
+  removeLinkPreview,
   resetLinkPreview,
 } from '../../services/LinkPreview';
 import { getMaximumAttachmentSize } from '../../util/attachments';
@@ -789,6 +790,10 @@ function replaceAttachments(
       return;
     }
 
+    if (hasDraftAttachments(attachments, { includePending: true })) {
+      removeLinkPreview();
+    }
+
     dispatch({
       type: REPLACE_ATTACHMENTS,
       payload: attachments.map(resolveDraftAttachmentOnDisk),