Document file scripting removal in breaking changes and remove file script references in documentation

[ppf2]

File scripts and related settings (eg. path.scripts) were deprecated in 5.5 and removed in 6.0+.

I think we will want to document this at https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking_60_scripting_changes.html and/or https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking_60_settings_changes.html.

We will also want to remove references to file scripts from various parts of the scripting documentation

• https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-scripting-using.html#modules-scripting-using-caching still mentions file scripts being cached
• https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-scripting-security.html#modules-scripting-security-do-no-weaken still mentions ES running filesystem scripts for default languages.

[rjernst]

Closed by #26579