arro3-io: Install numpy explicitly for the test run

0.9.0's tests import numpy directly. pyarrow no longer pulls it in, so
the cp314t test environment had none and collection failed.

Author: luhenry

.github/workflows/build-arro3-io.yml

@@ -107,7 +107,7 @@ jobs:
           # which has a riscv64 wheel, and source-builds them in the
           # container.
           CIBW_TEST_ENVIRONMENT: PIP_ONLY_BINARY=numpy,pyarrow
-          CIBW_TEST_REQUIRES: pytest pyarrow
+          CIBW_TEST_REQUIRES: pytest pyarrow numpy
           # cp311 has no riscv64 pyarrow wheel on our registry (pyarrow's
           # own riscv64 builds start at cp312), so the wheel still builds
           # on cp311 for the abi3 tag but isn't test-exercised there.