Fix clippy tests that trigger for_loop_over_fallibles lint

tests/ui/for_loop_unfixable.rs

@@ -8,6 +8,7 @@
     clippy::for_kv_map
 )]
 #[allow(clippy::linkedlist, clippy::unnecessary_mut_passed, clippy::similar_names)]
+#[allow(for_loop_over_fallibles)]
 fn main() {
     let vec = vec![1, 2, 3, 4];
 

tests/ui/for_loop_unfixable.stderr

@@ -1,5 +1,5 @@
 error: you are iterating over `Iterator::next()` which is an Option; this will compile but is probably not what you want
-  --> $DIR/for_loop_unfixable.rs:14:15
+  --> $DIR/for_loop_unfixable.rs:15:15
    |
 LL |     for _v in vec.iter().next() {}
    |               ^^^^^^^^^^^^^^^^^

tests/ui/for_loops_over_fallibles.rs

@@ -1,5 +1,6 @@
 #![warn(clippy::for_loops_over_fallibles)]
 #![allow(clippy::uninlined_format_args)]
+#![allow(for_loop_over_fallibles)]
 
 fn for_loops_over_fallibles() {
     let option = Some(1);