test: Ignore pretty-huge-vec.rs to fix nightlies

This ignores a test added in rust-lang#34639 because unfortunately the nightly bots are
now broken, but this is now tracked in rust-lang#34662.

Author: alexcrichton

src/test/debuginfo/pretty-huge-vec.rs

@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-test: FIXME(#34639)
 // ignore-windows failing on win32 bot
 // ignore-freebsd: gdb package too new
 // ignore-android: FIXME(#10381)