format code with gofumpt

gofumpt (https://github.com/mvdan/gofumpt) provides a supserset of `gofmt` / `go fmt`,
and addresses various formatting issues that linters may be checking for.

We can consider enabling the `gofumpt` linter to verify the formatting in CI, although
not every developer may have it installed, so for now this runs it once to get formatting
in shape.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

registry/proxy/proxymetrics.go

@@ -70,5 +70,4 @@ func init() {
 	pm.(*expvar.Map).Set("manifests", expvar.Func(func() interface{} {
 		return proxyMetrics.manifestMetrics
 	}))
-
 }