test: Remove support for Node 18 (#304)

Author: BilalQamar95

.github/workflows/ci.yml

@@ -11,16 +11,13 @@ on:
 jobs:
   tests:
     runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        node: [18, 20]
     steps:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Setup Nodejs
         uses: actions/setup-node@v4
         with:
-          node-version: ${{ matrix.node }}
+          node-version-file: '.nvmrc'
 
       - name: Install Dependencies
         run: npm ci