tests: add blank lines to test-topic-tutorial.t to fix .rst syntax This file is converted to .rst using docs/test2rst.py in a pretty simple and straightforward way, and it's possible to just embed chunks of reST inside the .t file. However, it's necessary to make sure these chunks follow the reST syntax (and that includes having blank lines after indented blocks. Noticed when building a .deb: sphinx complained "WARNING: Explicit markup ends without a blank line; unexpected unindent."