Custom field labels are not translated in element indexes

[angrybrad]

Environment:

• Craft version: 3.x
• PHP version: 7.x
• Database driver & version: n/a
• Plugins & versions:

Description:

In the new Customizable Element Indexes (CEI), it appears that field labels aren't translated – see http://cly.mmikkel.no/3P3v1F0a0R1y for an example (the value "field.label.featuredImage" is found in /translations/{locale}.php and is translated everywhere else throughout the CP but here).

[brandonkelly]

Not able to reproduce this in v2 or v3. Custom field labels are getting translated properly in both the Customize modal and the table headers.