cosmetic/rich_media/parser: fix typo

lib/pleroma/web/rich_media/parser.ex

@@ -96,7 +96,7 @@ defp parse_uri(true, url) do
     |> validate_page_url
   end
 
-  defp parse_uri(_, _), do: {:error, "not an URL"}
+  defp parse_uri(_, _), do: {:error, "not a URL"}
 
   defp get_tld(host) do
     host

test/pleroma/web/rich_media/parser_test.exs

@@ -121,13 +121,13 @@ test "refuses to crawl plain HTTP and other scheme URL" do
       res = Parser.parse(url)
 
       assert {:error, {:url, "scheme mismatch"}} == res or
-               {:error, {:url, "not an URL"}} == res
+               {:error, {:url, "not a URL"}} == res
     end)
   end
 
   test "refuses to crawl malformed URLs" do
     url = "example.com[]/ogp"
-    assert {:error, {:url, "not an URL"}} == Parser.parse(url)
+    assert {:error, {:url, "not a URL"}} == Parser.parse(url)
   end
 
   test "refuses to crawl URLs of private network from posts" do