[SPARK-20400][DOCS] Remove References to 3rd Party Vendor Tools

## What changes were proposed in this pull request?

Simple documentation change to remove explicit vendor references.

## How was this patch tested?

NA

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: anabranch <bill@databricks.com>

Closes #17695 from anabranch/remove-vendor.

docs/configuration.md

@@ -2270,8 +2270,8 @@ should be included on Spark's classpath:
 * `hdfs-site.xml`, which provides default behaviors for the HDFS client.
 * `core-site.xml`, which sets the default filesystem name.
 
-The location of these configuration files varies across CDH and HDP versions, but
-a common location is inside of `/etc/hadoop/conf`. Some tools, such as Cloudera Manager, create
+The location of these configuration files varies across Hadoop versions, but
+a common location is inside of `/etc/hadoop/conf`. Some tools create
 configurations on-the-fly, but offer a mechanisms to download copies of them.
 
 To make these files visible to Spark, set `HADOOP_CONF_DIR` in `$SPARK_HOME/spark-env.sh`