Fix openwrt wget fail (#33)

Openwrt use Busbox version, which don't support -t. Also we don't really neet `-t` to retry twice to download.

agent/install.sh

@@ -141,7 +141,7 @@ install() {
         NZ_AGENT_URL="https://${GITHUB_URL}/naibahq/agent/releases/download/${_version}/nezha-agent_${os}_${os_arch}.zip"
     fi
 
-    _cmd="wget -t 2 -T 60 -O /tmp/nezha-agent_${os}_${os_arch}.zip $NZ_AGENT_URL >/dev/null 2>&1"
+    _cmd="wget -T 60 -O /tmp/nezha-agent_${os}_${os_arch}.zip $NZ_AGENT_URL >/dev/null 2>&1"
     if ! eval "$_cmd"; then
         err "Download nezha-agent release failed, check your network connectivity"
         exit 1