[MINOR][DOCS] Fix Jenkins job badge image and link in README.md

### What changes were proposed in this pull request?

This PR proposes to fix the Jenkins job badge:

Before:

![Screen Shot 2020-12-16 at 4 14 14 PM](https://user-images.githubusercontent.com/6477701/102316960-2c9ebe80-3fba-11eb-878d-07ae735fb3a6.png)

After:

![Screen Shot 2020-12-16 at 4 14 09 PM](https://user-images.githubusercontent.com/6477701/102316956-2a3c6480-3fba-11eb-9fa4-b8312edb8a1a.png)

### Why are the changes needed?

To make people can easily check the status of builds.

### Does this PR introduce _any_ user-facing change?

No, dev-only.

### How was this patch tested?

Manually tested via using GitHub.

Closes apache#30797 from HyukjinKwon/minor-readme.

Authored-by: HyukjinKwon <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

README.md

@@ -9,7 +9,7 @@ and Structured Streaming for stream processing.
 
 <https://spark.apache.org/>
 
-[![Jenkins Build](https://amplab.cs.berkeley.edu/jenkins/job/spark-master-test-sbt-hadoop-2.7-hive-2.3/badge/icon)](https://amplab.cs.berkeley.edu/jenkins/job/spark-master-test-sbt-hadoop-2.7-hive-2.3)
+[![Jenkins Build](https://amplab.cs.berkeley.edu/jenkins/job/spark-master-test-sbt-hadoop-3.2/badge/icon)](https://amplab.cs.berkeley.edu/jenkins/job/spark-master-test-sbt-hadoop-3.2)
 [![AppVeyor Build](https://img.shields.io/appveyor/ci/ApacheSoftwareFoundation/spark/master.svg?style=plastic&logo=appveyor)](https://ci.appveyor.com/project/ApacheSoftwareFoundation/spark)
 [![PySpark Coverage](https://img.shields.io/badge/dynamic/xml.svg?label=pyspark%20coverage&url=https%3A%2F%2Fspark-test.github.io%2Fpyspark-coverage-site&query=%2Fhtml%2Fbody%2Fdiv%5B1%5D%2Fdiv%2Fh1%2Fspan&colorB=brightgreen&style=plastic)](https://spark-test.github.io/pyspark-coverage-site)