[release/2.14] Sync test channel CUDA/ROCm arches with what 2.14 builds

Follow-up to #8495, which bumped `CURRENT_CANDIDATE_VERSION` to 2.14.0 but
left the arch dicts on their 2.13-era values. The test channel now serves
2.14.0 release candidates, so its arch lists must match what
`pytorch/pytorch` release/2.14 actually builds:

    CUDA_ARCHES = ["12.6", "13.0", "13.2", "13.4"]
    ROCM_ARCHES = ["7.2", "7.14"]

Changes:

- `CUDA_ARCHES_DICT["test"]`: add `13.4`. Without it the cu134 RC wheels are
  never validated.
- `ROCM_ARCHES_DICT["test"]`: `7.1, 7.2` -> `7.2, 7.14`. `7.1` is not built
  for 2.14, so validation would look for wheels that do not exist and miss
  rocm7.14 entirely.
- `PYTHON_ARCHES_DICT["test"]` already matches nightly; unchanged.

The `release` channel entries are deliberately left alone -- they still
describe GA 2.13 and move as part of the 2.14 go-live step.

Test plan:
- `python -m tools.tests.test_generate_binary_build_matrix` - 11 tests pass.
- `--update-reference-files` produces no asset changes.
- Generated linux wheel matrix, before -> after:
  - test: cuda +cu134, rocm 7.1 -> 7.14 (`stable_version` already 2.14.0)
  - release: unchanged (2.13.0, cu126/130/132, rocm7.1/7.2)
  - nightly: unchanged

Authored with the assistance of Claude Code.

Author: atalman

tools/scripts/generate_binary_build_matrix.py

@@ -45,13 +45,13 @@
 }
 CUDA_ARCHES_DICT = {
     "nightly": ["12.6", "13.0", "13.2", "13.4"],
-    "test": ["12.6", "13.0", "13.2"],
+    "test": ["12.6", "13.0", "13.2", "13.4"],
     "release": ["12.6", "13.0", "13.2"],
 }
 
 ROCM_ARCHES_DICT = {
     "nightly": ["7.2", "7.14"],
-    "test": ["7.1", "7.2"],
+    "test": ["7.2", "7.14"],
     "release": ["7.1", "7.2"],
 }