Upgrade to Node 20

.github/workflows/ci.yaml

@@ -22,5 +22,5 @@ jobs:
       - name: Disable core.autocrlf on Windows
         if: runner.os == 'Windows'
         run: git config --global core.autocrlf false
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: ./.

action.yml

@@ -39,5 +39,5 @@ inputs:
       version of fourmolu you wish to use.
     default: latest
 runs:
-  using: 'node16'
+  using: 'node20'
   main: 'dist/index.js'

index.js

@@ -2,7 +2,6 @@ import * as path from 'path';
 import * as fs from 'fs';
 
 const core = require('@actions/core');
-const github = require('@actions/github');
 const httpm = require('@actions/http-client');
 const tool_cache = require('@actions/tool-cache');
 const exec = require('@actions/exec');