Update DEVGUIDE.md (#5741)
Update DEVGUIDE.md (#5741)

Explicitly mention that the optional components are found in the VS Installer, not somewhere on the downloads page (since that's what was linked just before)
brettfo/visualfsharp,dsyme/fsharp,brettfo/visualfsharp,brettfo/visualfsharp,dsyme/fsharp,dsyme/fsharp,brettfo/visualfsharp,syeerzy/visualfsharp,dsyme/fsharp,syeerzy/visualfsharp,dsyme/fsharp,cloudRoutine/FSharp.Compiler.Service,cloudRoutine/FSharp.Compiler.Service,cloudRoutine/FSharp.Compiler.Service,syeerzy/visualfsharp,syeerzy/visualfsharp,syeerzy/visualfsharp,brettfo/visualfsharp,brettfo/visualfsharp,dsyme/fsharp,syeerzy/visualfsharp,dsyme/fsharp