Add if: always() because 2.4.x's make check failed on snapshot [ci skip]

`check-snapshot-ruby_2_4` uses `make test` instead of `make check`.
95692e54f4/.github/workflows/snapshot.yml (L448-L449)

`draft-release` use `make check` to make it simple, and
actions is required regardless of success or failure.

On the other hand, snapshot success can be ignored,
so normally it should not fail.

.github/workflows/draft-release.yml

@@ -129,8 +129,10 @@ jobs:
         run: cd ruby-*/ && make $JOBS check TESTOPTS="-q --tty=no" MSPECOPT="-ff"
       - name: make install
         run: cd ruby-*/ && sudo make $JOBS install
+        if: always() # `make check` may fail when 2.4.x
       - name: ruby -v
         run: ruby -v
+        if: always() # `make check` may fail when 2.4.x
       - uses: k0kubun/action-slack@v2.0.0
         with:
           payload: |