CI: Use checkout v3 for erlang < 20.3, and v4 for newer ones

actions/checkout@v4 updated from node16 to node20,
which requires a recent GLIBC 2.27 or 2.28,
however some old erlang container images include too old GLIBC

.github/workflows/hexpm-release.yml

@@ -12,7 +12,7 @@ jobs:
       image: erlang:26
     steps:
       - name: Check out
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Setup rebar3 hex
         run: |