Require GPyTorch>=1.15.1. (#3184)

Summary:
 ---

Pull Request resolved: #3184

Reviewed By: Balandat

Differential Revision: D93482264

Pulled By: saitcakmak

fbshipit-source-id: 0fd21fc06d75f9e7dbcc7a45504bc80799a67d09

Author: saitcakmak

pyproject.toml

@@ -23,7 +23,7 @@ dynamic = ["version"]
 dependencies = [
     "typing_extensions",
     "pyre_extensions",
-    "gpytorch>=1.14.2",
+    "gpytorch>=1.15.1",
     "linear_operator>=0.6",
     "torch>=2.2",
     "pyro-ppl>=1.8.4",