Fix cosmetic problems in YAML source

This change corrects problems reported by the `yamllint` linter.

Since key duplication problems were removed in 4d48711, this commit
mainly fixes trailing spaces and extra empty lines at beginning/end of
files.

test/integration/targets/postgresql/tasks/main.yml

@@ -879,4 +879,3 @@
 - assert:
     that:
       - "result.stdout_lines[-1] == '(0 rows)'"
-