[SPARK-32247][INFRA] Install and test scipy with PyPy in GitHub Actions

### What changes were proposed in this pull request?

This PR proposes to install `scipy` as well in PyPy. It will test several ML specific test cases in PyPy as well. For example, https://github.com/apache/spark/blob/31a16fbb405a19dc3eb732347e0e1f873b16971d/python/pyspark/mllib/tests/test_linalg.py#L487

It was not installed when GitHub Actions build was added because it failed to install for an unknown reason. Seems like it's fixed in the latest scipy.

### Why are the changes needed?

To improve test coverage.

### Does this PR introduce _any_ user-facing change?

No, dev-only.

### How was this patch tested?

GitHub Actions build in this PR will test it out.

Closes #30054 from HyukjinKwon/SPARK-32247.

Authored-by: HyukjinKwon <gurwls223@apache.org>
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>

.github/workflows/build_and_test.yml

@@ -147,12 +147,11 @@ jobs:
     - name: Install Python packages (Python 2.7 and PyPy3)
       if: contains(matrix.modules, 'pyspark')
       # PyArrow is not supported in PyPy yet, see ARROW-2651.
-      # TODO(SPARK-32247): scipy installation with PyPy fails for an unknown reason.
       run: |
         python2.7 -m pip install numpy 'pyarrow<3.0.0' pandas scipy xmlrunner
         python2.7 -m pip list
         # PyPy does not have xmlrunner
-        pypy3 -m pip install numpy pandas
+        pypy3 -m pip install numpy pandas scipy
         pypy3 -m pip list
     - name: Install Python packages (Python 3.8)
       if: contains(matrix.modules, 'pyspark') || (contains(matrix.modules, 'sql') && !contains(matrix.modules, 'sql-'))