fix dockerfile typo error

Author: QiJune

Dockerfile

@@ -13,7 +13,7 @@ ARG WITH_DOC
 ARG WITH_STYLE_CHECK
 
 ENV WOBOQ OFF
-ENV WITH_GPU=${WITH_AVX:-OFF}
+ENV WITH_GPU=${WITH_GPU:-OFF}
 ENV WITH_AVX=${WITH_AVX:-ON}
 ENV WITH_DOC=${WITH_DOC:-OFF}
 ENV WITH_STYLE_CHECK=${WITH_STYLE_CHECK:-OFF}