MM-19872: Update dependencies for enterprise implementation of new SAML2 golib. (#13298)

* Update dependencies for enterprise implementation of new SAML2 golib.

* add indirect

vendor/github.com/mattermost/gosaml2/attribute.go

@@ -0,0 +1,19 @@
+package saml2
+
+import "github.com/mattermost/gosaml2/types"
+
+// Values is a convenience wrapper for a map of strings to Attributes, which
+// can be used for easy access to the string values of Attribute lists.
+type Values map[string]types.Attribute
+
+// Get is a safe method (nil maps will not panic) for returning the first value
+// for an attribute at a key, or the empty string if none exists.
+func (vals Values) Get(k string) string {
+	if vals == nil {
+		return ""
+	}
+	if v, ok := vals[k]; ok && len(v.Values) > 0 {
+		return string(v.Values[0].Value)
+	}
+	return ""
+}