chore(pkg-tests.sh): delete dead code

scripts/pkg-tests.sh

@@ -21,6 +21,8 @@ esac
 PACKAGE_NAME="${1}"
 PACKAGE_TYPE="${2}"
 ARCH="${3}"
+# Needed by deploy/package/**/Makefile
+export ARCH
 
 export DEBUG=1
 export CODE_PATH=${CODE_PATH:-"/emqx"}
@@ -49,22 +51,6 @@ if ! [ -f "$PACKAGE_FILE" ]; then
     exit 1
 fi
 
-if [ -z "$ARCH" ]
-then
-  case "$(uname -m)" in
-    x86_64)
-      ARCH='amd64'
-      ;;
-    aarch64)
-      ARCH='arm64'
-      ;;
-    arm*)
-      ARCH=arm
-      ;;
-  esac
-fi
-export ARCH
-
 emqx_prepare(){
     mkdir -p "${PACKAGE_PATH}"