Fix typo in HOT template guide

Under the "Template input parameters" section, there was a typo in the
following sentence:
"For example, the following definition for the instance_type parameter
would select the ‘m1.small’ flavor unless specified otherwise be the
user."

Closes-Bug: 1339269
Change-Id: I59a170407669c74d23f36b232b3d492e52ce5eac
Merge "Fix typo in HOT template guide"