Updates can_run function signature for forceatlas2_layout (rapidsai#158)

Updates `can_run` function signature for `forceatlas2_layout` to add missing `dtype` arg. This fixes a test failure in `test_match_signature_and_names` which now runs for `forceatlas2_layout` due to it being supported in NX 3.5.

Authors:
  - Rick Ratzel (https://github.com/rlratzel)
  - Ralph Liu (https://github.com/nv-rliu)

Approvers:
  - Vyas Ramasubramani (https://github.com/vyasr)

URL: rapidsai#158

Author: rlratzel