Align gleam version in GH workflow with Docker base image, update erlef/setup-beam + otp-version for latest ubuntu

Author: pascalwengerter

.github/workflows/test.yml

@@ -11,9 +11,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2.0.0
-      - uses: erlef/setup-beam@v1.13.0
+      - uses: erlef/setup-beam@v1.15.2
         with:
-          otp-version: "23.2"
-          gleam-version: "0.25.0"
+          otp-version: "25.0"
+          gleam-version: "0.25.3"
       - run: gleam format --check src test
       - run: gleam test