Update hardware cloud tutorial (DO NOT MERGE UNTIL SEPTEMBER 21ST) (#743

)

* update hardware cloud tutorial

* Update doc/introduction/photonic_hardware.rst

doc/introduction/photonic_hardware.rst

@@ -7,7 +7,7 @@ photonic hardware or to be run on a cloud simulator via the Xanadu Cloud.
 .. warning::
 
  An API key is required to communicate with the hardware locally.
- Set up a `Xanadu Cloud <https://cloud.xanadu.ai>`__ account for free, and generate
+ `Contact us <mailto:hardware-access@xanadu.ai>`__ to set up an account and generate
  your `cloud API key <https://strawberryfields.ai/photonics/demos/tutorial_X8.html#configuring-your-credentials>`__.
 
 Configuring your account