[SPARK-27601][BUILD] Upgrade stream-lib to 2.9.6

## What changes were proposed in this pull request?

[stream-lib 2.9.6](https://github.com/addthis/stream-lib/commits/v2.9.6) include several improvements:
![image](https://user-images.githubusercontent.com/5399861/56938062-7eb77580-6b32-11e9-8c36-711ab943d657.png)

## How was this patch tested?

N/A

Closes #24492 from wangyum/SPARK-27601.

Authored-by: Yuming Wang <yumwang@ebay.com>
Signed-off-by: Sean Owen <sean.owen@databricks.com>

dev/deps/spark-deps-hadoop-2.7

@@ -186,7 +186,7 @@ spire-macros_2.12-0.13.0.jar
 spire_2.12-0.13.0.jar
 stax-api-1.0-2.jar
 stax-api-1.0.1.jar
-stream-2.7.0.jar
+stream-2.9.6.jar
 stringtemplate-3.2.1.jar
 super-csv-2.2.0.jar
 univocity-parsers-2.7.3.jar

dev/deps/spark-deps-hadoop-3.2

@@ -206,7 +206,7 @@ spire-macros_2.12-0.13.0.jar
 spire_2.12-0.13.0.jar
 stax-api-1.0.1.jar
 stax2-api-3.1.4.jar
-stream-2.7.0.jar
+stream-2.9.6.jar
 stringtemplate-3.2.1.jar
 super-csv-2.2.0.jar
 token-provider-1.0.1.jar

pom.xml

@@ -604,7 +604,7 @@
       <dependency>
         <groupId>com.clearspring.analytics</groupId>
         <artifactId>stream</artifactId>
-        <version>2.7.0</version>
+        <version>2.9.6</version>
         <exclusions>
           <!-- Only HyperLogLogPlus is used, which doesn't depend on fastutil -->
           <exclusion>