xhtml_style: fix invisible cursor in textarea with chrome
With chrome ( 85.0.4183.108 but I think it appears a few weeks/months ago ) when using erp5_xhtml_style when the cursor in the first column on the left it's not visible, because the bold background hides it.
Default user agent spreadsheet is a 2px padding, but we have a rule applying a padding 0 for all textarea. Revert this rule for textarea used as fields in content.
The cursor is in Description field, left to "This style is ..." but cannot be seen.
The cursor is same location (Description field, left to "This style is ...") and this time is visible.