Fix another typo in RuntimeError (#2706)

Co-authored-by: Kaiwen Wu <[email protected]>

Author: benediktjohannes

gpytorch/variational/ciq_variational_strategy.py

@@ -342,6 +342,6 @@ def __call__(self, x: torch.Tensor, prior: bool = False, diag: bool = True, **kw
                 )
             else:
                 raise RuntimeError(
-                    f"Invalid variational distribuition ({type(variational_dist_u)}). "
+                    f"Invalid variational distribution ({type(variational_dist_u)}). "
                     "Expected a multivariate normal or a delta distribution."
                 )