fix documents pdf preview using invalid text base64

Author: owenisas

frontend/src/components/app/views/DocumentsView.tsx

@@ -65,7 +65,7 @@ function statusLabel(status?: string | null): string {
 function docToAttachedFile(doc: UserDocument): AttachedFile {
   const ext = (doc.name || "").split(".").pop()?.toLowerCase() ?? ""
   const isTextViewable = [
-    "txt", "md", "tex", "csv", "tsv", "rtf", "pdf",
+    "txt", "md", "tex", "csv", "tsv", "rtf",
     ...(SUPPORTED_EXTENSIONS.code as readonly string[]),
   ].includes(ext)