[CI] Pin schemathesis<4 to fix test_openai_schema.py collection failure

schemathesis v4 (released 2025-06-10) removed the `GenerationConfig`
class from its public API.  The test imports it as
`from schemathesis import GenerationConfig`, which breaks at collection
time with `ImportError: cannot import name 'GenerationConfig'`.

The requirements files specified `schemathesis>=3.39.15` with no upper
bound, so CI resolves the latest (v4.x) and fails.  Pin to `<4` in all
four input/unpinned requirements files (cuda.in, rocm.in, xpu.in,
nightly-torch.txt) to keep the v3 API the test relies on.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Tyler Michael Smith <tlrmchlsmth@gmail.com>

requirements/test/cuda.in

@@ -40,7 +40,7 @@ lm-eval[api]>=0.4.12 # required for model evaluation test
 mteb[bm25s]>=2, <3 # required for mteb test
 transformers==5.5.3
 tokenizers==0.22.2
-schemathesis>=3.39.15 # Required for openai schema test.
+schemathesis>=3.39.15,<4 # Required for openai schema test.
 # quantization
 bitsandbytes==0.49.2
 buildkite-test-collector==0.1.9

requirements/test/nightly-torch.txt

@@ -31,7 +31,7 @@ lm-eval[api]>=0.4.12 # required for model evaluation test
 mteb[bm25s]>=2, <3 # required for mteb test
 transformers==5.5.3
 tokenizers==0.22.2
-schemathesis>=3.39.15 # Required for openai schema test.
+schemathesis>=3.39.15,<4 # Required for openai schema test.
 # quantization
 bitsandbytes>=0.49.2
 buildkite-test-collector==0.1.9

requirements/test/rocm.in

@@ -39,7 +39,7 @@ lm-eval[api]>=0.4.12 # required for model evaluation test
 mteb[bm25s]>=2, <3 # required for mteb test
 transformers==5.5.3
 tokenizers==0.22.2
-schemathesis>=3.39.15 # Required for openai schema test
+schemathesis>=3.39.15,<4 # Required for openai schema test
 # quantization
 bitsandbytes==0.49.2
 buildkite-test-collector==0.1.9

requirements/test/xpu.in

@@ -27,7 +27,7 @@ soundfile
 blobfile
 rapidfuzz
 gpt-oss
-schemathesis
+schemathesis>=3.39.15,<4
 jiwer
 bm25s
 pystemmer