Fix SynExpr.ImplicitZero doc comment (#7831)
Fix SynExpr.ImplicitZero doc comment (#7831)

ImplicitZero is also used in error recovery during parsing, and the current comment contradicts it.
cloudRoutine/FSharp.Compiler.Service,dsyme/fsharp,dsyme/fsharp,cloudRoutine/FSharp.Compiler.Service,dsyme/fsharp,dsyme/fsharp,dsyme/fsharp,dsyme/fsharp,dsyme/fsharp,cloudRoutine/FSharp.Compiler.Service