Suppress inline warning

Without this suppression, building the code prints:
```
frameworks/base/packages/SystemUI/src/com/android/systemui/util/kotlin/nullability.kt:29:1: warning: expected performance impact from inlining is insignificant. Inlining works best for functions with parameters of functional types
inline fun <T> Optional<T>.getOrNull(): T? = orElse(null)
^
```

Reviewing the documentation here:
https://kotlinlang.org/docs/inline-functions.html

It seems that the inline warning fires if there are no inlinable
function parameters and no reified type parameters, as is the case here.
However the original author of the code still thinks this is a
reasonable target for inlining as a short method and a common utility,
and I don't disagree.

I'm suppressing the warning because it seems to be unhelpful, and
because build warnings are considered tech debt as per:
go/battledroids#clean-up-build-warnings

Test: built, warning no longer appears
Bug: 217776569
Change-Id: Ic94f4e7d1612679c67e7aaaa46dc884f2f60b7d4