Don't print backtrace on ICEs in issue-86800.rs.

Because it then just has to be filtered out.

This change makes this test more like these other tests:
- tests/ui/treat-err-as-bug/err.rs
- tests/ui/treat-err-as-bug/delay_span_bug.rs
- tests/ui/mir/validate/storage-live.rs
- tests/ui/associated-inherent-types/bugs/ice-substitution.rs
- tests/ui/layout/valid_range_oob.rs

tests/ui/impl-trait/issues/issue-86800.rs

@@ -1,14 +1,12 @@
 #![feature(type_alias_impl_trait)]
 
 // edition:2021
-// unset-rustc-env:RUST_BACKTRACE
 // compile-flags:-Z treat-err-as-bug=1
-// error-pattern:stack backtrace:
+// error-pattern: aborting due to `-Z treat-err-as-bug=1`
 // failure-status:101
-// normalize-stderr-test "note: .*" -> ""
-// normalize-stderr-test "thread 'rustc' .*" -> ""
-// normalize-stderr-test " +[0-9]+:.*\n" -> ""
-// normalize-stderr-test " +at .*\n" -> ""
+// normalize-stderr-test ".*note: .*\n\n" -> ""
+// normalize-stderr-test "thread 'rustc' panicked.*\n" -> ""
+// rustc-env:RUST_BACKTRACE=0
 
 use std::future::Future;
 

tests/ui/impl-trait/issues/issue-86800.stderr

@@ -1,24 +1,12 @@
 error: unconstrained opaque type
-  --> $DIR/issue-86800.rs:33:34
+  --> $DIR/issue-86800.rs:31:34
    |
 LL | type TransactionFuture<'__, O> = impl '__ + Future<Output = TransactionResult<O>>;
    |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = 
-
-
-stack backtrace:
-
 error: the compiler unexpectedly panicked. this is a bug.
 
-
-
-
-
-
-
 query stack during panic:
 #0 [type_of] computing type of `TransactionFuture::{opaque#0}`
 #1 [check_mod_item_types] checking item types in top-level module
-#2 [analysis] running analysis passes on this crate
 end of query stack