Fix type expressed in last example of specs' Floating-point numbers (fixes 370) (#371)
Fix type expressed in last example of specs' Floating-point numbers (fixes 370) (#371)

According to the specs, aithmetic operations applied to a mixture of `float`
and `int` operands should result in a `float` value. However, the example
`3.0 // 2.0` had the value `1` commented beside it, which could imply
that its type is `int`. For clarity this mistake was fixed.
google/starlark-go,google/starlark-go