Pin pandas < 2

Pandas is expecting to release v2 in two weeks (pandas-dev/pandas#46776 (comment)). But we are still incompatible with their main branch: 
- #7441 
- #7420

This PR pins pandas to `<2`

setup.cfg

@@ -76,7 +76,7 @@ include_package_data = True
 python_requires = >=3.9
 install_requires =
     numpy >= 1.21  # recommended to use >= 1.22 for full quantile method support
-    pandas >= 1.4
+    pandas >= 1.4, <2
     packaging >= 21.3
 
 [options.extras_require]