Those keys at the start and end is created by the exporter to prevent the Godot importer from deleting the bones.
Most 3D exporters will make these keys. It is part of the rigging workflow. Most software will delete bones that have no animation.
If the bones are really unimportant delete them before export.
If they are important, like they keep other bones attached or they are rig bones, then you actually want the keys.
In Blender, each bone has a "deform" setting, you can remove that check mark. Then when exporting select "Exclude Control Bones" and it will automatically delete the bones.