Revert "exclude problematic test"

This reverts commit 3f1e156.

Author: marcoieni

tests/rustdoc-ui/issues/issue-98690.rs

@@ -0,0 +1,10 @@
+//@ compile-flags: --test --persist-doctests /../../ -Z unstable-options
+//@ failure-status: 101
+//@ only-linux
+
+#![crate_name = "foo"]
+
+//! ```rust
+//! use foo::dummy;
+//! dummy();
+//! ```

tests/rustdoc-ui/issues/issue-98690.stderr

@@ -0,0 +1 @@
+Couldn't create directory for doctest executables: Permission denied (os error 13)