fix typo in docker-env.mk
fix typo in docker-env.mk

Signed-off-by: Wang Zhuo <ad087d73797577a2edf5aef8b766590b3f283860@outlook.com>

jimthematrix/fabric,manish-sethi/fabric,jimthematrix/fabric,hyperledger/fabric,hyperledger/fabric,manish-sethi/fabric