Updated docstring.

test/test_mat_mul_precision.py

@@ -1,14 +1,6 @@
-"""Numeric tests for default precision of mat mul.
-
-There are three similar test files, suffixed default, high, and highest.
-Unfortunately, the precision cannot reliably
-be dynamically changed between tensor operations, so
-the tests are split into three files to ensure a fresh
-environment for each test.
-"""
+"""Numeric tests for default precision of mat mul."""
 
 import unittest
-import time
 
 import torch
 import torch_xla