This test checks the suggested fix to remove unused require statements from
go.mod files.

-- flags --
-write_sumfile=a

-- proxy/example.com@v1.0.0/x.go --
package pkg
const X = 1

-- a/go.mod --
module mod.com

go 1.14

require example.com v1.0.0 //@quickfix("require", re"not used", a)

-- @a/a/go.mod --
@@ -4,3 +4 @@
-
-require example.com v1.0.0 //@quickfix("require", re"not used", a)
-
-- a/main.go --
package main
func main() {}