[flame_3d] Fix unrelated broken tests on main due to bug on drawRawAtlas

### What happened?

The tests flagged on [this PR](https://github.com/flame-engine/flame/pull/3299) do not work on Flutter main.
That has nothing to do with Flame 3D but it is breaking our build.

### What do you expect?

Tests to pass.

### How can we reproduce this?

_No response_

### What steps should take to fix this?

_No response_

### Do have an example of where the bug occurs?

_No response_

### Relevant log output

_No response_

### Execute in a terminal and put output into the code block below

Output of: flutter doctor -v

### Affected platforms

All

### Other information

_No response_

### Are you interested in working on a PR for this?

- [ ] I want to work on this