Fix syntax error re: new p5.Vector.cross

[lindapaiste]

Fixes the failing tests explained in this comment:

All of the tests related to the camera _orbit method fail with TypeError: _main.default.Vector.cross is not a constructor because the code uses improper syntax new p5.Vector.cross(up, front). cross is a static method so there shouldn't be a new there.

Changes:

• Replace syntax new p5.Vector.cross(a, b) with p5.Vector.cross(a, b) in a few places in the p5.Camera class.
• A bunch of tests which were failing before will pass now.

PR Checklist

• npm run lint passes
• Inline documentation is included / updated
• Unit tests are included / updated

[limzykenneth]

Looks good. Thanks!