Fix term name

Author: stevepiercy

docs/i18n-l10n/contributing-translations.md

@@ -48,7 +48,7 @@ The process of translating Plone Classic UI is the following.
 
 3.  Either update or create a translation.
 
-    -   To _update_ an existing translation, translate the {term}`po` files under your language of choice at `plone/app/locales/locales/{language_code}/LC_MESSAGES/*.po`.
+    -   To _update_ an existing translation, translate the {term}`PO file`s under your language of choice at `plone/app/locales/locales/{language_code}/LC_MESSAGES/*.po`.
     In Classic UI, we have several language files because some of the original messages are spread over several language domains and products.
     -   To _create_ a translation, create a new directory at `plone/app/locales/locales/{language_code}/LC_MESSAGES`, copy all the `.pot` files in `plone/app/locales/locales` to your new directory, rename the files in your directory by changing the file extension to `.po`, and start translating.