fix incorrect URL in purchase example
fix incorrect URL in purchase example

chtyim/cdap,caskdata/cdap,caskdata/cdap,mpouttuclarke/cdap,caskdata/cdap,anthcp/cdap,mpouttuclarke/cdap,hsaputra/cdap,anthcp/cdap,chtyim/cdap,hsaputra/cdap,chtyim/cdap,caskdata/cdap,chtyim/cdap,caskdata/cdap,anthcp/cdap,hsaputra/cdap,hsaputra/cdap,anthcp/cdap,anthcp/cdap,chtyim/cdap,mpouttuclarke/cdap,caskdata/cdap,chtyim/cdap,mpouttuclarke/cdap,mpouttuclarke/cdap,hsaputra/cdap