Fix broken TestGetPost (#29228)

* Fix broken TestGetPost

* Skip TestPromoteGuestToUser/websocket_update_user_event

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/api4/post_test.go

@@ -2805,6 +2805,11 @@ func TestGetPost(t *testing.T) {
 
 		_, err = client.RemoveUserFromChannel(context.Background(), th.BasicChannel.Id, th.BasicUser.Id)
 		require.NoError(t, err)
+		t.Cleanup(func() {
+			// Add the user back to the channel
+			_, _, err = client.AddChannelMember(context.Background(), th.BasicChannel.Id, th.BasicUser.Id)
+			require.NoError(t, err)
+		})
 
 		// Channel is public, should be able to read post
 		_, _, err = c.GetPost(context.Background(), th.BasicPost.Id, "")