Small changes to handle the last line in the diff library, LSP tests,
and diff to text edits conversion.
Fixesgolang/go#30137
Change-Id: Iff0e53a04c2dabf6f54eb7c738b4c0837f16efba
Reviewed-on: https://go-review.googlesource.com/c/162217
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Cottrell <iancottrell@google.com>