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

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

Jenkins link in README.md is currently broken:

![Screen Shot 2020-01-21 at 3 11 10 PM](https://user-images.githubusercontent.com/6477701/72779777-678c5b00-3c60-11ea-8523-9d82abc0493e.png)

Seems new jobs are configured to test Hive 1.2 and 2.3 profiles. The link pointed out `spark-master-test-maven-hadoop-2.7` before. Now it become two.

```
spark-master-test-maven-hadoop-2.7 -> spark-master-test-maven-hadoop-2.7-hive-2.3
                                      spark-master-test-maven-hadoop-2.7-hive-1.2
```

Since the PR builder uses Hive 2.3 by default, this PR fixes the link to point out `spark-master-test-maven-hadoop-2.7-hive-2.3`

### Why are the changes needed?

To fix the image and broken link.

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

No. Dev only change.

### How was this patch tested?

Manually clicking.

Closes apache#27301 from HyukjinKwon/minor-link.

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/badge/icon)](https://amplab.cs.berkeley.edu/jenkins/job/spark-master-test-sbt-hadoop-2.7)
+[![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)
 [![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)