MM-51699: Skip flaky test (#22635)

https://mattermost.atlassian.net/browse/MM-51699

```release-note
NONE
```

server/boards/app/boards_test.go

@@ -140,6 +140,7 @@ func TestAddMemberToBoard(t *testing.T) {
 }
 
 func TestPatchBoard(t *testing.T) {
+	t.Skip("MM-51699")
 	th, tearDown := SetupTestHelper(t)
 	defer tearDown()