docs/F#StyleGuide: prefer Mutable to 'Scg' [no ci]

Author: knocte

docs/FSharpStyleGuide.md

@@ -17,7 +17,7 @@ different things).
 NOTE: To be able to comply with the rule above, it is important that you do NOT
 `open System.Collections.Generics`, otherwise the name `List` will be the mutable
 list instead of the F#'s immutable one. If you really really need to access the
-former, use `type ScgList<'T> = System.Collections.Generics.List<'T>` instead.
+former, use `type MutableList<'T> = System.Collections.Generics.List<'T>` instead.
 * To not confuse array types with lists, we prefer to use `List.Empty` over `[]`
 (where it's possible; e.g. in match cases it's not possible), and `array<Foo>`
 over `Foo []`.