Linear regression Tutorial link (#6468)
Linear regression Tutorial link (#6468)

* Fixing a link in the linear regression tutorial.

The link was initally going to mxnet-test.readthedocs.io. Changed it to mxnet.io/api.

* More appropriate language.

Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet