Consider removing confirmation dialog before removing entries

[delphinus]

Some strange behavior like #270 are caused by the confirmation dialog before removing old entries from DB. This behavior has been existing from the original telescope-frecency, but I think we should remove this dialog because it causes several problems.

Concretely, I will remove db_safe_mode option and make it default to remove stale entries without confirmation.

[delphinus]

This comment is a simple note:

The strangely typed A mentioned in #270 is caused by this code.

https://github.com/nvim-telescope/telescope.nvim/blob/2eca9ba22002184ac05eddbe47a7fe2d5a384dfc/lua/telescope/pickers.lua#L595-L604