[TensorDock] Remove the tensordock from supported backeds #3092

Added TODO

Author: peterschmidt85

src/dstack/_internal/core/backends/tensordock/models.py

@@ -4,6 +4,8 @@
 
 from dstack._internal.core.models.common import CoreModel
 
+# TODO: TensorDock is deprecated and will be removed in the future
+
 
 class TensorDockAPIKeyCreds(CoreModel):
     type: Annotated[Literal["api_key"], Field(description="The type of credentials")] = "api_key"