Fix equality comparison for StringText
Fix equality comparison for StringText

This being a container for a source string, while identical StringTexts will  have the same GetHashCode(), it fails for equality testing because a StringText object is compared to the other's source text, which is always false.

The comparison to string behavior is retained.

dsyme/fsharp,dsyme/fsharp,dsyme/fsharp,dsyme/fsharp,dsyme/fsharp,dsyme/fsharp,dsyme/fsharp