docs: Fix step 2 of space shooter tutorial delta values

[FlorianGrollich]

Description

There was a small code Error in Step 2 of the Space Shooter Tutorial

the onPanUpdate method looked like this 
  void onPanUpdate(DragUpdateInfo info) {
    player.move(info.delta.global);
  }

but it should look like this

  void onPanUpdate(DragUpdateInfo info) {
    player.move(info.delta.global);
  }

Checklist

• I have followed the Contributor Guide when preparing my PR.
• [-] I have updated/added tests for ALL new/updated/fixed functionality.
• [-] I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• [-] I have updated/added relevant examples in examples or docs.

Breaking Change?

• Yes, this PR is a breaking change.
• No, this PR is not a breaking change.

Related Issues

Closes #3199