[Doc] Document serverless flag in databricks_pipeline (#3797)

## Changes
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With GA of Serverless DLT pipelines we need to add this flag to the
documentation

## Tests
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- [ ] `make test` run locally
- [x] relevant change in `docs/` folder
- [ ] covered with integration tests in `internal/acceptance`
- [ ] relevant acceptance tests are passing
- [ ] using Go SDK

Author: alexott

docs/resources/pipeline.md

@@ -78,9 +78,10 @@ The following arguments are supported:
 * `continuous` - A flag indicating whether to run the pipeline continuously. The default value is `false`.
 * `development` - A flag indicating whether to run the pipeline in development mode. The default value is `true`.
 * `photon` - A flag indicating whether to use Photon engine. The default value is `false`.
+* `serverless` - An optional flag indicating if serverless compute should be used for this DLT pipeline.  Requires `catalog` to be set, as it could be used only with Unity Catalog.
 * `catalog` - The name of catalog in Unity Catalog. *Change of this parameter forces recreation of the pipeline.* (Conflicts with `storage`).
 * `target` - The name of a database (in either the Hive metastore or in a UC catalog) for persisting pipeline output data. Configuring the target setting allows you to view and query the pipeline output data from the Databricks UI.
-* `edition` - optional name of the [product edition](https://docs.databricks.com/data-engineering/delta-live-tables/delta-live-tables-concepts.html#editions). Supported values are: `CORE`, `PRO`, `ADVANCED` (default).
+* `edition` - optional name of the [product edition](https://docs.databricks.com/data-engineering/delta-live-tables/delta-live-tables-concepts.html#editions). Supported values are: `CORE`, `PRO`, `ADVANCED` (default).  Not required when `serverless` is set to `true`.
 * `channel` - optional name of the release channel for Spark version used by DLT pipeline.  Supported values are: `CURRENT` (default) and `PREVIEW`.
 
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