test: ignore backoff's asyncio.iscoroutinefunction warning on 3.14

The backoff dependency calls asyncio.iscoroutinefunction in its
on_exception decorator; Python 3.14 deprecates it (removal in 3.16).
The SDK's own code uses inspect.iscoroutinefunction, and at runtime this
is only a warning. Filter it (alongside the existing get_event_loop_policy
ignore) so warnings-as-errors doesn't fail the suite until backoff updates.

Refs SLS-265

Author: deanq

pytest.ini

@@ -2,9 +2,11 @@
 addopts = --durations=10 --cov-config=.coveragerc --timeout=120 --timeout_method=thread --cov=runpod --cov-report=xml --cov-report=term-missing --cov-fail-under=90 -p no:cacheprovider -p no:unraisableexception
 filterwarnings =
     error
-    # nest_asyncio (test-only dep) calls the deprecated asyncio.get_event_loop_policy
-    # on Python 3.14; the SDK itself does not. Don't fail collection on its warning.
+    # Third-party deps (e.g. backoff) still call asyncio APIs that 3.14 deprecates
+    # and slates for removal in 3.16. The SDK's own code does not; at runtime these
+    # only warn. Don't fail the suite on them until the deps update.
     ignore:'asyncio\.get_event_loop_policy' is deprecated:DeprecationWarning
+    ignore:'asyncio\.iscoroutinefunction' is deprecated:DeprecationWarning
 python_files = tests.py test_*.py *_test.py
 norecursedirs = venv *.egg-info .git build tests/e2e
 asyncio_mode = auto