Clean and filter out any lines that are that are identical

Some lines in the .po files appear to duplicate the English string into the translated string. This almost certainly adds noise to training so we should filter them out.

```
> #: client/blocks/login/login-form.jsx:214
> msgid "By logging in via any of the options below, you agree to our {{tosLink}}Terms of Service{{/tosLink}}."
> msgstr "By logging in via any of the options below, you agree to our {{tosLink}}Terms of Service{{/tosLink}}."
```

Start by locating the code that reads and prepares the .po files for training, then inspect how msgid and msgstr values are compared. Done means entries whose translated string is identical to the English string are excluded, including cases like the example shown.

Written by the indexing model from the issue text.