fix(serverHandler/asset): render asset without condition

As `http.ServerContent` has its own logic for detecting request method
and skip output content body for `HEAD` method, remove custom detection
logic.

Author: marjune163

src/serverHandler/asset.go

@@ -8,7 +8,5 @@ func (h *handler) asset(w http.ResponseWriter, r *http.Request, assetPath string
 	header := w.Header()
 	header.Set("X-Content-Type-Options", "nosniff")
 	header.Set("Cache-Control", "public, max-age=3600")
-	if needResponseBody(r.Method) {
-		h.theme.RenderAsset(w, r, assetPath)
-	}
+	h.theme.RenderAsset(w, r, assetPath)
 }