(#8792) Rename basic smoke test to reflect file_line rename

Without this patch the basic smoke test in the module tests/ directory
did not math up with the renamed whole_line => file_line resource type.

This patch updates the smoke test file to match the most recently
selected name of file_line.  The filename has been changed, comments
added to the smoke test file, and resource declarations inside the file
changed.

tests/file_line.pp

@@ -1,7 +1,9 @@
+# This is a simple smoke test
+# of the file_line resource type.
 file { '/tmp/dansfile':
   ensure => present
 }->
-whole_line { 'dans_line':
+file_line { 'dans_line':
   line => 'dan is awesome',
   path => '/tmp/dansfile',
 }