Update src/test/ui/pattern/issue-53820-slice-pattern-large-array.rs

Co-Authored-By: Mazdak Farrokhzad <twingoow@gmail.com>

Author: Nadrieril

src/test/ui/pattern/issue-53820-slice-pattern-large-array.rs

@@ -1,4 +1,7 @@
 // check-pass
+
+// This used to cause a stack overflow in the compiler.
+
 #![feature(slice_patterns)]
 
 fn main() {