Fix RateLimitPerUser on ChannelEdit (#1152)

* fix ability to turn off slowmode via ChannelEdit

* fix(structs): gofmt

Co-authored-by: Cyrus <50967051+Not-Cyrus@users.noreply.github.com>

structs.go

@@ -360,7 +360,7 @@ type ChannelEdit struct {
 	UserLimit            int                    `json:"user_limit,omitempty"`
 	PermissionOverwrites []*PermissionOverwrite `json:"permission_overwrites,omitempty"`
 	ParentID             string                 `json:"parent_id,omitempty"`
-	RateLimitPerUser     int                    `json:"rate_limit_per_user,omitempty"`
+	RateLimitPerUser     *int                   `json:"rate_limit_per_user,omitempty"`
 
 	// NOTE: threads only