Overzealous narrowing warning now error

[agcapps]

https://github.com/Alpine-DAV/ascent/blob/e504a28c7a1a6d89b40fa9db17a19fc21d1e7b35/src/libs/dray/rendering/renderer.cpp#L353

Here, my compiler errors out because e.g. 0.1 * 2.0 - 1.0 is a double literal getting stored as a float32. The compiler suggests using static_cast<float32>( ).

Grumpy, because I see no harm, but the compiler treats it as an error.