Typo in file documentation for lib/bats/helpers

The top level file comment mentions:

```
#   . "path/to/bats/helpers"
#   set_bats_suite_name "${BASH_SOURCE[0]%/*}"
#   remove_bats_test_dirs
```

It should be `set_bats_test_suite_name` rather than `set_bats_suite_name`.