Update test.yml to remove 1.18 (#558)

Author: justinpolygon

.github/workflows/test.yml

@@ -13,7 +13,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        go-version: [1.18.x, 1.19.x, 1.20.x, 1.21.x]
+        go-version: [1.19.x, 1.20.x, 1.21.x]
     name: go-test
     runs-on: ${{ matrix.os }}
     steps: