Remove docs, use ubuntu-latest

Author: ewels

.github/workflows/build.yml

@@ -14,7 +14,7 @@ jobs:
   build:
     name: Nextflow website build
     if: "!contains(github.event.head_commit.message, '[ci skip]')"
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     timeout-minutes: 10
     strategy:
       fail-fast: false