Link with a fixed text (fixed_text_file_url) has no schema defined

Problem/Motivation

To translate "Link text", it's necessary to do it through the "config_translation" module. For that is needed a schema definition in *.schema.yml file. For "Link with fixed text (fixed_text_link)" formatter it's created but for "Link with a fixed text (fixed_text_file_url)" formatter it's not.

Proposed resolution

Create a definition for "Link with a fixed text (fixed_text_file_url)" in fixed_text_link_formatter.schema.yml.