tests: handle missing pandas gracefully

Pandas is not yet ready for Python 3.11.  Use pytest.importorskip()
to skip that one regression test that requires it when it's not
available to unblock rapidfuzz on py3.11 on Gentoo.

tests/test_process.py

@@ -5,7 +5,6 @@
 import pytest
 
 from rapidfuzz import process_py, process_cpp, fuzz
-import pandas as pd
 
 
 class process:
@@ -298,6 +297,7 @@ def testNullStrings(self):
 
     def testIssue81(self):
         # this mostly tests whether this segfaults due to incorrect ref counting
+        pd = pytest.importorskip("pandas")
         choices = pd.Series(
             ["test color brightness", "test lemon", "test lavender"],
             index=[67478, 67479, 67480],