refactor(python): drop now-always-true build.if

python-release.yml only triggers on workflow_dispatch, so build.if:
github.event_name == 'workflow_dispatch' is always true and redundant; remove it
(the exact event set is already pinned in the spec). Update the spec assertion
accordingly.

.github/workflows/python-release.yml

@@ -25,7 +25,6 @@ concurrency:
 jobs:
   build:
     name: Build four wheels
-    if: github.event_name == 'workflow_dispatch'
     uses: ./.github/workflows/build-exe-for-python-sdk.yml
     with:
       targets: node24-linux-x64,node24-linux-arm64,node24-macos-arm64