Cleanup superfluous dependabot configurations

[abelsromero]

Each branch has a dependabot configuration. In some cases, some branches have conflicting configurations.
We should be able to handle them all only in the main branch.

We already removed it from the 2.0.x branch, now we need to handle it in other branches.

Branches to apply:

• 2.0.x #782
• 1.6.x #786
• 1.5.x #787
• 1.4.x #788