rustc_lint: remove superfluous assertion

`Option::unwrap` is called on the next line.

compiler/rustc_lint/src/late.rs

@@ -33,7 +33,6 @@ use std::cell::Cell;
 /// Extract the `LintStore` from the query context.
 /// This function exists because we've erased `LintStore` as `dyn Any` in the session.
 pub fn unerased_lint_store(sess: &Session) -> &LintStore {
-    assert!(sess.lint_store.is_some());
     let store: &Lrc<_> = sess.lint_store.as_ref().unwrap();
     let store: &dyn Any = &**store;
     store.downcast_ref().unwrap()