Restricting mpmath <= 1.3

Summary:
This commit restricts `mpmath` to versions `<=1.3`, since the latest alpha release breaks `sympy` -> `pytorch` -> `gpytorch` -> `botorch`.

See also sympy/sympy#26273 and [the commit removing `rational` from `mpmath`](mpmath/mpmath@721e257).

Reviewed By: Balandat

Differential Revision: D54214691

fbshipit-source-id: 759d4d4f1ee6178cf7ab0f2b3c9596a0ffde21c4

requirements.txt

@@ -1,5 +1,6 @@
 multipledispatch
 scipy
+mpmath>=0.19,<=1.3
 torch>=1.13.1
 pyro-ppl>=1.8.4
 gpytorch==1.11