Fix removing vendor directories in estimate

Only devendor the repo dir, otherwise it fails with a permission denied error

estimate.go

@@ -99,7 +99,7 @@ func estimate(importpath string) error {
 		return fmt.Errorf("go get: %w", err)
 	}
 
-	found, err := removeVendor(gopath)
+	found, err := removeVendor(repodir)
 	if err != nil {
 		return fmt.Errorf("remove vendor: %w", err)
 	}