Fix the "portion vs. serving" wording issue

[tanius]

Describe the bug

In the OpenFoodFacts app's tab "Nutrition", using the English localization, there is a line saying "Per portion: 250 ml". This is inconsistent wording given that one line below the same thing is called "serving":

In addition, the line "Per portion: […]" is formatted like a title for the table below it. That's not its role, so this choice of style is confusing.

Expected behavior

Using the same word for the same thing. And using formatting that makes clear that "Per portion: […]" is a note and refers to the "Per serving" column just below. As a proposal, it may look like this:

Smartphone

• Device: Asus Nexus 7
• OS: Android 6.0.1

[tanius]

As of today, this issue is still open – it still looks as in the first screenshot in version 3.4.8 (which is the newest version in Google Play right now).