Update dex to get rid of vulnerable goxml

go.mod

@@ -3,7 +3,7 @@ module github.com/sky-uk/osprey
 require (
 	github.com/SermoDigital/jose v0.9.1
 	github.com/coreos/go-oidc v2.2.1+incompatible
-	github.com/dexidp/dex v0.0.0-20190418222123-60f47c4228b7
+	github.com/dexidp/dex v2.13.0+incompatible
 	github.com/golang-jwt/jwt v3.2.2+incompatible
 	github.com/golang/protobuf v1.5.2
 	github.com/jaytaylor/html2text v0.0.0-20211105163654-bc68cce691ba
@@ -39,6 +39,7 @@ require (
 	github.com/inconshreveable/mousetrap v1.0.0 // indirect
 	github.com/jonboulle/clockwork v0.2.2 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/kylelemons/godebug v1.1.0 // indirect
 	github.com/mattn/go-runewidth v0.0.13 // indirect
 	github.com/matttproud/golang_protobuf_extensions v1.0.1 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect