fix(serve): pin pandas below 3.1.0 to unblock serve unit tests (#6524)

* fix(serve): pin pandas to 2.x in test extra to unblock unit tests

The sagemaker-serve unit-tests job runs py310/py311/py312 tox envs.
pandas is pulled in transitively (via mlflow) and is unpinned, so pip
resolves the newly released pandas 3.1.0 on py311/py312 (3.x requires
Python >=3.11). That build leaves the C extensions unbuilt in CI
("ImportError: C extension: None not built"), so pytest fails at
collection and the whole job goes red — even though py310 (pandas 2.3.3)
passes all tests. This is environment/dependency churn, unrelated to any
product change.

Pin pandas to the 2.x line in the test extra so all three envs resolve
the known-good 2.3.3 (what py310 already uses). Verified locally:
`pandas>=2.3.0,<3` resolves to 2.3.3 and imports cleanly on Python 3.12.

* fix(serve): cap pandas below 3.1.0 (last-known-good 3.0.6)

Refine the pin to the last-known-good state: before pandas 3.1.0 was
released, the py311/py312 unit-test envs resolved pandas 3.0.6 and passed;
py310 resolves 2.3.3 (pandas 3.x requires Python >=3.11). 3.1.0's wheels
are built against a newer NumPy C-ABI than those envs resolve, so it fails
to import at collection. `>=2.3.0,<3.1.0` restores py311/py312 to 3.0.6
and keeps py310 on 2.3.3 -- exactly the configuration that was green
before the 3.1.0 release. A hard ==3.0.6 is intentionally avoided because
it would break the py310 env.

---------

Co-authored-by: Roja Reddy Sareddy <rsareddy@amazon.com>

Author: rsareddy0329

sagemaker-serve/pyproject.toml

@@ -69,6 +69,13 @@ test = [
     "onnxruntime",
     "torch>=2.0.0",
     "tritonclient[http]",
+    # pandas is pulled in transitively (e.g. via mlflow). Cap below 3.1.0:
+    # pandas 3.1.0 ships wheels built against a newer NumPy C-ABI than the
+    # py311/py312 test envs resolve, so it fails to import ("ImportError:
+    # C extension: None not built") at pytest collection time. The previous
+    # release 3.0.6 was passing on py311/py312; py310 stays on the 2.x line
+    # (2.3.3) because pandas 3.x requires Python >=3.11.
+    "pandas>=2.3.0,<3.1.0",
 ]
 dev = [
     "pytest",