tools/relnotes: use types from work-stats package

We can save a little code by borrowing logic from my work-stats package.
It's not strictly necessary, but it might make things a little easier.
(Maybe we could move the work-stats stuff into this repo).

Change-Id: I0a6c63360fbddd34c714ade1c9cfbb5d14dd6d8d
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/337495
Trust: Rebecca Stambler <rstambler@golang.org>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Suzy Mueller <suzmue@golang.org>

Author: stamblerre

go.mod

@@ -2,4 +2,7 @@ module github.com/golang/vscode-go
 
 go 1.16
 
-require golang.org/x/build v0.0.0-20210617174213-df58bbac082b
+require (
+	github.com/stamblerre/work-stats v0.0.0-20210726215650-a14fc877fae7
+	golang.org/x/build v0.0.0-20210722210716-65acb205e577
+)