[FIX] Prevent pushing translation for technical attributes add via view inehritance

When exporting translation of an XML view, any text of the tag `<attribute>` is exported even if it is a technical attribute like 'context' or 'attrs'. For example, the module the translation template of the module `account_analytic_analysis` has many terms like `{'required': [('type','=','contract')],...`.

This patch only limits the export to only translatable attributes like 'string' or 'palceholder'.