hack/vendor.sh: run "go mod tidy" before vendoring

The hack/vendor.sh script is used to (re)vendor dependencies. However, it did
not run `go mod tidy` before doing so, wheras the vendor _validation_ script
did.

This could result in vendor validation failing if go mod tidy resulted in
changes (which could be in `vendor.sum`).

In "usual" situations, this could be easily done by the user (`go mod tidy`
before running `go mod vendor`), but due to our (curent) uses of `vendor.mod`,
and having to first set up a (dummy) `go.mod`, this is more complicated.

Instead, just make the script do this, so that `hack/vendor.sh` will always
produce the expected result.

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

hack/validate/vendor

@@ -3,11 +3,6 @@
 SCRIPTDIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 source "${SCRIPTDIR}/.validate"
 
-go_mod_tidy(){
-	${SCRIPTDIR}/../go-mod-prepare.sh
-	GO111MODULE=auto go mod tidy -modfile 'vendor.mod' -compat 1.17
-}
-
 validate_vendor_diff(){
 	IFS=$'\n'
 	check_files=( 'vendor.sum' 'vendor.mod' 'vendor/' )
@@ -54,6 +49,5 @@ validate_vendor_used() {
 	done
 }
 
-go_mod_tidy
 validate_vendor_diff
 validate_vendor_used