stop dependabot

[bourgeoa]

dependabot has some drawbacks :

• updates only on main. which makes staging behind main
• lot of noise : many messages
• updates everything including devdependencies which may not need any updating
• can introduce worms due the number of touched dependencies

Manual updates seems to be preferred for now.
This need to be done before new releases.

This can be reviewed again when the the project will be less active