Breakpoint is not being hit in ServiceParsedInputOps.fs

[auduchinok]

Not sure if it's fixed by #12018, but it was on main branch from a few days ago inside VisualFSharp.sln.

[dsyme]

This is a bug in ValidateBreakpointLocation. Because the binding is let f = function ... this is correctly treated in codegen as if it is defining a local function, and we don't normally allow breakpoints on let f x = ... because there is no code to break on for the definition of f itself (only its body).