GH-51208: [CI][Python] Update builds to CPython 3.15.0rc2 (cp315)

[paultiq]

Rationale for this change

#48191 added 3.15 to CI, but pins to rc1 in a few places.

rc2 is now available, this is a minimal update from rc1 to rc2.

What changes are included in this PR?

Moves pin from rc1 to rc2 in the dockerfiles and install_python.sh

Are these changes tested?

Tested the manylinux build

Are there any user-facing changes?

No

• GitHub Issue: [CI][Python] Update Python builds to Release Candidate 2 of cp315 (3.15.0rc2) #51208

[github-actions]

⚠️ GitHub issue #51208 has been automatically assigned in GitHub to PR creator.

[raulcd]

Thanks for working on this!
Could you try bumping the underlying images to build the wheels to use the newer cpython there?

diff --git a/compose.yaml b/compose.yaml
index b44d8c836a..6bca6e1ba4 100644
--- a/compose.yaml
+++ b/compose.yaml
@@ -1180,7 +1180,7 @@ services:
       args:
         arch: ${ARCH}
         arch_short: ${ARCH_SHORT}
-        base: quay.io/pypa/manylinux_2_28_${ARCH_ALIAS}:2026.08.08-1
+        base: quay.io/pypa/manylinux_2_28_${ARCH_ALIAS}:2026.09.05-1
         manylinux: 2_28
         python: ${PYTHON}
         python_abi_tag: ${PYTHON_ABI_TAG}
@@ -1205,7 +1205,7 @@ services:
       args:
         arch: ${ARCH}
         arch_short: ${ARCH_SHORT}
-        base: quay.io/pypa/musllinux_1_2_${ARCH_ALIAS}:2026.08.08-1
+        base: quay.io/pypa/musllinux_1_2_${ARCH_ALIAS}:2026.09.05-1
         musllinux: 1_2
         python: ${PYTHON}
         python_abi_tag: ${PYTHON_ABI_TAG}

I'll kick off some sanity wheel builds after that and merge if no CI issues

[paultiq]

Done, also checked my notes from preview PR #48191 and caught a few other needed changes: PYTHON_WHEEL_WINDOWS_IMAGE_REVISION
PYTHON_WHEEL_WINDOWS_TEST_IMAGE_REVISION

and the Python build_date

[raulcd]

@github-actions crossbow submit wheel-cp315

[github-actions]

Revision: f73bb30

Submitted crossbow builds: ursacomputing/crossbow @ actions-2f019ffc35

Task	Status
wheel-macos-monterey-cp315-cp315-amd64
wheel-macos-monterey-cp315-cp315-arm64
wheel-macos-monterey-cp315-cp315t-amd64
wheel-macos-monterey-cp315-cp315t-arm64
wheel-manylinux-2-28-cp315-cp315-amd64
wheel-manylinux-2-28-cp315-cp315-arm64
wheel-manylinux-2-28-cp315-cp315t-amd64
wheel-manylinux-2-28-cp315-cp315t-arm64
wheel-musllinux-1-2-cp315-cp315-amd64
wheel-musllinux-1-2-cp315-cp315-arm64
wheel-musllinux-1-2-cp315-cp315t-amd64
wheel-musllinux-1-2-cp315-cp315t-arm64
wheel-windows-cp315-cp315-amd64
wheel-windows-cp315-cp315t-amd64