actions: it makes more sense to use Haxe version matrix on samples

.github/workflows/main.yml

@@ -781,11 +781,14 @@ jobs:
   neko-samples:
     needs: package-haxelib
     runs-on: ubuntu-20.04
+    strategy:
+      matrix:
+        haxe-version: [3.4.7, 4.0.5, 4.1.5, 4.2.5, 4.3.1]
     steps:
 
       - uses: krdlab/setup-haxe@v1
         with:
-          haxe-version: 4.2.5
+          haxe-version: ${{ matrix.haxe-version }}
 
       - name: Set HAXEPATH
         run: |