Set Channel Topic

{
	"ok": true,
	"channel": {
		"id": "<string>",
		"name": "<string>",
		"is_channel": true,
		"is_group": false,
		"is_im": false,
		"is_mpim": false,
		"is_private": false,
		"created": 937729381,
		"is_archived": false,
		"is_general": false,
		"unlinked": 0,
		"name_normalized": "<string>",
		"is_shared": false,
		"is_org_shared": false,
		"is_pending_ext_shared": false,
		"pending_shared": [],
		"context_team_id": "<string>",
		"updated": 2332800365955,
		"parent_conversation": null,
		"creator": "<string>",
		"is_ext_shared": false,
		"shared_team_ids": [
			"<string>"
		],
		"pending_connected_team_ids": [],
		"is_member": false,
		"topic": {
			"value": "<string>",
			"creator": "<string>",
			"last_set": 2749117283
		},
		"purpose": {
			"value": "<string>",
			"creator": "<string>",
			"last_set": 1
		},
		"previous_names": []
	},
	"warning": "<string>",
	"response_metadata": {
		"warnings": [
			"<string>"
		]
	}
}