Remove redundant iter test

[davidhewitt]

This test produces extra "Exception state should not be set." output, which I found confusing.

$ cargo test --test test_various incorrect
    Finished test [unoptimized + debuginfo] target(s) in 0.02s
     Running target/debug/deps/test_various-756839897d6f2700

running 1 test
Exception state should not be set.
test incorrect_iter ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 7 filtered out

It's also redundant as the following test checks exactly the same behaviour:

pyo3/src/types/iterator.rs

Lines 183 to 184 in 3809e2b

	#[test]
	fn int_not_iterable() {

[kngwyu]

Good catch, thank you!