Actually rename modelbridge to adapter everywhere (#2850)

Summary:
Pull Request resolved: #2850

X-link: facebook/Ax#3773

See title.

Reviewed By: dme65

Differential Revision: D74441007

fbshipit-source-id: e06f450028257c83d7952f5b5b12e45e537a275a

Author: Balandat

tutorials/batch_mode_cross_validation/batch_mode_cross_validation.ipynb

@@ -15,7 +15,7 @@
     "\n",
     "$$y = \\sin(2\\pi x) + \\epsilon, ~\\epsilon \\sim \\mathcal N(0, 0.2).$$\n",
     "\n",
-    "Note: this tutorial aims to introduce batch-mode regression and evaluation in GPyTorch with CV as an example application. For alternative, more user-friendly functions to perform CV in Ax, see [ax.modelbridge.cross_validation](https://github.com/facebook/Ax/blob/main/ax/modelbridge/cross_validation.py). However, for larger CV tasks, it may be useful to exploit GPyTorch batch-mode, as shown in this tutorial."
+    "Note: this tutorial aims to introduce batch-mode regression and evaluation in GPyTorch with CV as an example application. For alternative, more user-friendly functions to perform CV in Ax, see [ax.adapter.cross_validation](https://github.com/facebook/Ax/blob/main/ax/adapter/cross_validation.py). However, for larger CV tasks, it may be useful to exploit GPyTorch batch-mode, as shown in this tutorial."
    ]
   },
   {