Fix docs wordings (#11226)

* Fix "part of Arrow" wording in docs

DataFusion is a top level project.

* Fix doc reference in into_optimized_plan

Author: findepi

datafusion/core/src/dataframe/mod.rs

@@ -1157,7 +1157,7 @@ impl DataFrame {
     /// Return the optimized [`LogicalPlan`] represented by this DataFrame.
     ///
     /// Note: This method should not be used outside testing -- see
-    /// [`Self::into_optimized_plan`] for more details.
+    /// [`Self::into_unoptimized_plan`] for more details.
     pub fn into_optimized_plan(self) -> Result<LogicalPlan> {
         // Optimize the plan first for better UX
         self.session_state.optimize(&self.plan)

docs/source/user-guide/introduction.md

@@ -22,7 +22,7 @@
 DataFusion is a very fast, extensible query engine for building
 high-quality data-centric systems in [Rust](http://rustlang.org),
 using the [Apache Arrow](https://arrow.apache.org) in-memory format.
-DataFusion is part of the [Apache Arrow](https://arrow.apache.org/)
+DataFusion originated as part of the [Apache Arrow](https://arrow.apache.org/)
 project.
 
 DataFusion offers SQL and Dataframe APIs, excellent [performance](https://benchmark.clickhouse.com/), built-in support for CSV, Parquet, JSON, and Avro, [python bindings], extensive customization, a great community, and more.