internal/lsp: don't send diagnostics for old file versions
internal/lsp: don't send diagnostics for old file versions

This isn't a strictly necessary change, but it simplifies things for
open files when the initial workspace load diagnostics come in too late.

Updates golang/go#36452

Change-Id: I85a9c201876b7c63a97d8dca020fc396b3c57706
Reviewed-on: https://go-review.googlesource.com/c/tools/+/213820
Run-TryBot: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Heschi Kreinick <e89ab2b172855aa0ad01c40c4d8a3535a61ac68a@google.com>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools