fix(image): enable verifying certificate for centos7
diff --git a/docker/pegasus-build-env/centos7/Dockerfile b/docker/pegasus-build-env/centos7/Dockerfile
index eb9e2dc..7902682 100644
--- a/docker/pegasus-build-env/centos7/Dockerfile
+++ b/docker/pegasus-build-env/centos7/Dockerfile
@@ -49,7 +49,7 @@
                    krb5-devel \
                    cyrus-sasl-devel \
                    patch; \
-		   yum -y install ca-certificates; \
+                   yum -y install ca-certificates; \
                    yum clean all; \
                    rm -rf /var/cache/yum;