[FIX] charts: remove "Show values" for trendlines

[rrahir]

Showing the values of the trendlines is both useless, as they are not actual data, and bloating the chart with a huge amount text, making the chart very hard to read.

Task: 4104524

Description:

description of this task, what is implemented and why it is implemented that way.

Task: : TASK_ID

review checklist

• [ ] feature is organized in plugin, or UI components
• [ ] support of duplicate sheet (deep copy)
• [ ] in model/core: ranges are Range object, and can be adapted (adaptRanges)
• [ ] in model/UI: ranges are strings (to show the user)
• [ ] undo-able commands (uses this.history.update)
• [ ] multiuser-able commands (has inverse commands and transformations where needed)
• [ ] new/updated/removed commands are documented
• [ ] exportable in excel
• [ ] translations (_t("qmsdf %s", abc))
• [ ] unit tested
• [ ] clean commented code
• [ ] track breaking changes
• [ ] doc is rebuild (npm run doc)
• [ ] status is correct in Odoo

[robodoo]