test: Ignore issue-19501 pretty for now

I don't have enough time to investigate this thoroughly, so for now let's get
the queue moving by ignoring this test.

cc #19501

Author: alexcrichton

src/test/run-pass-fulldeps/issue-13560.rs

@@ -11,6 +11,7 @@
 // aux-build:issue-13560-1.rs
 // aux-build:issue-13560-2.rs
 // aux-build:issue-13560-3.rs
+// ignore-pretty FIXME #19501
 // ignore-stage1
 
 // Regression test for issue #13560, the test itself is all in the dependent