Shorten long doc

[plutasnyy]

Removed copy-paste of the same documentation.

Reduced token cost per using client by:

# Total Tokens: 16665 - main
# Total tokens: 14868 - pluto/reduce_prompt_length_2_one_custom_node_doc

Assumption:

• The update tool has to be loaded into the context with the create workflow tool

The good:

• it works

The bad:

• update function doesn't know the current state state of the workflow, so if we use 'custom' workflow, we have to pass config for entire 'workflow', because there is no 'patch' it is full replacement. To make it work update function has to be called in the same context with create, or get_workflow_info has to be called first (I guess). I tested previously, and saying 'call this tool first' is not going to work.
  Anyway, this pull request doesn't introduce regression in that area, just some small limitations.

[plutasnyy]

Changelog will be bumped