Remove "impacted files" copy from <details> element

[codecovdesign]

Problem to solve

In the details section of PR comment "Impacted files" can cause confusion - consider cases when all changed files are covered, or alternative like this scenario below when some files are missing coverage, user may thing the "impacted.." in details may be more files and/or that it's separate from what we show which is actually changed files.

Solution

• remove "impacted files" from <details>