Nullability mismatch in non-ref foreach cannot be suppressed

[jjonescz]

Originally posted by @TessenR in #73928 (comment)

Is it expected that now you can suppress nullability mismatch for foreach with ref variables but not for foreach with regular variables?

It looks like the following test is supposed to cover that scenario, but it's missing the actual nullability mismatch because the parameter of the test method is object[] instead of object?[]

9941c1f#diff-14fe026e6093e9522c01e6c377b26554dd6b663214884198dcc244f370548fa1R90883

The following code right now does have a warning and it cannot be suppressed:

void M2(object?[] a) { foreach (object item in a!) { } }

[alrz]

This looks very much like #38586